The Immune Responses (M) Flashcards
What is adaptive system and what is its purpose?
It is developed in a host primarily to protect the host from harmful effects of pathogens and other foreign substances
What are the 2 types of adaptive response?
1) Antibody-mediated (humoral)
2) Cell-mediated (cellular)
What is humoral adaptive response (actions brought by this response are to what)?
It acts mainly against extracellular pathogens, or those pathogen that infects outside a host cell
What is cellular adaptive response (action of this response is to what)?
It acts against intracellular pathogens, or those pathogens that infect host cells
What are the 2 important components in humoral immunity?
1) Antibodies
2) Complement
* hence, humoral immunity is based on the action of these components
What type of bacteria does humoral immunity react to?
1) Extracellular bacteria
2) Bacteria whose virulence is due to polysaccharide capsules
What are the examples of extracellular bacteria (being acted upon by humoral immunity)?
1) Corynebacterium diphtheriae
2) Clostridium tetani
What are the examples of bacteria having polysaccharide capsules (being acted upon by humoral immunity)?
1) Haemophilus influenzae
2) Neisseria meningitidis
3) Streptococcus pneumoniae
Does humoral immunity also acts to viruses?
Yes
Humoral immunity acts to viruses that have the capability to infect what organs / parts of the human body?
Viruses that can infect through:
1) Respiratory tract
2) Intestinal tract
Humoral immunity also participates in the pathogenesis of what?
Hypersensitivity reactions and certain autoimmune diseases
What is the main feature of humoral immune responses?
Antibody production
What are the different phases in the process of production of Abs?
1) Lag phase
2) Log phase
3) Plateau
4) Decline phase
What is lag phase (and its characteristics)?
1) It is the immediate phase following exposure to Ag
2) During this phase, no Abs are detected in the circulation
What is log phase (and its characteristics)?
1) It is the phase next to lag phase
2) It is characterized by a steady rise in Ab titers in the circulation
What is plateau (and its characteristics)?
It is a phase of equilibrium bet Ab synthesis and catabolism
What is decline phase (and its characteristics)?
It is characterized by an increase in the catabolism of Abs compared to the production of Abs, leading to a fall in Ab titer in the circulation
What are the 2 types of humoral response?
1) Primary response
2) Secondary response
What are the characteristics of primary response (humoral response)?
1) Ab is detectable after a longer lag period than the secondary response
2) Lag period is typically 7 - 10 days or longer depending on the nature of Ag, the dose of Ag, and the route of administration (oral or parenteral)
3) Slow, sluggish, and short-lived Abs
4) Low Ab titer
5) IgM is the 1st Ab to be formed, followed by IgG, IgA, or both
6) IgM lvls tend to decline sooner as compared to IgG lvls
Do primary response (in humoral response) have a longer or shorter lag period?
Longer
If primary response (in humoral response) has a longer lag period (than secondary response of humoral immunity), how long is the lag period? And if primary response (in humoral response) has a shorter lag period (than secondary response of humoral immunity), how short is the lag period?
The lag period of primary response (of humoral immunity) is longer compared to the lag period of secondary response (of humoral immunity), the lag period is typically 7 - 10 days or longer
What is the basis of duration (for Ags) of lag phase (in primary response of humoral response)?
Depending on the:
1) Nature of Ag
2) The dose of Ag
3) The route of administration
What are the different methods of route of administration of Ag (where the period of lag phase is dependent on; primary response of humoral immunity)?
1) Oral
2) Parenteral
What Ig is 1st to be formed in the lag phase of primary response (in humoral immunity)?
IgM
What is the order of production of Igs that are formed in the lag phase of primary response (in humoral immunity)?
1) IgM
2) IgG
3) IgA
2. 1 / 3.1) Both IgG and IgA
W/c Ig tends to decline sooner in the lag phase of primary response (in humoral immunity)?
IgM lvls tend to decline sooner as compared to IgG lvls
What are the characteristics of secondary response (of humoral immunity)?
1) Rapid Ab response due to 2nd encounter w/ the same Ag, or a closely related “cross-reacting” Ag
2) Lag period is typically very short (3 - 5 days)
3) Prompt, powerful, and prolonged response
4) Higher lvl of Abs for longer period
5) Predominantly IgG
6) These changes in secondary response are attributed to the persistence of Ag-specific “memory cells” following the 1st contact w/ the Ag
7) These memory cells proliferate in large #s to produce large clones of specific B cells and plasma cells that mediate the secondary response
Why does rapid Ab response occur in the secondary response (of humoral immunity)?
Due to the 2nd encounter w/ the same Ag, or a closely related “cross-reacting” Ag
Is the lag period in secondary response (of humoral immunity) short or long?
Short, typically very short
If secondary response (in humoral response) has a longer lag period (than primary response of humoral immunity), how long is the lag period? Or if secondary response (in humoral response) has a shorter lag period (than primary response of humoral immunity), how short is the lag period?
The lag period of secondary response (of humoral immunity) is shorter (or very short) compared to the lag period of primary response (of humoral immunity), the lag period is typically very short having 3 - 5 days
What is the predominant type of Ig present in the lag phase of secondary response (of humoral immunity)?
IgG
What type of cells are responsible for occurrence of changes of secondary response (of humoral immunity) from primary response (of humoral immunity)?
Memory cells
True or False.
Memory cells are not Ag-specific. Why or why not?
False, because memory cells are Ag-specific
What is the purpose of memory cells’ proliferation (or memory cells itself)?
These memory cells proliferate in large #s to produce large clones of specific B cells and plasma cells that mediate the secondary response
What are the types of cells that mediate the secondary response (of humoral immunity)?
1) Specific B cells
2) Plasma cells
Synthesis and production of Abs typically is dependent to what?
It is dependent to the complex interaction of 3 cells
What are the 3 types of cells that are being dependent on when it comes to synthesis and production of Abs?
1) Macrophages
2) Helper T cells
3) B cells
What is the meaning of APC?
Antigen presenting cells
What is the purpose of APCs?
To present Ags to immunocompetent cells
What are the examples of APCs?
1) Macrophages
2) Dendritic cells
What happens after the processing of Ags by macrophage?
The fragments of Ag appear on the surfaces of macrophage in association w/ class II MHC proteins
What is the purpose of Ag-class II MHC protein complex?
Binds to specific receptors present on the surface of Th cells (helper T cells)
What is the purpose of Th cells?
To produce cytokines
What is the purpose of cytokines (being produced by Th cells)?
To activate B cells
What is the purpose of B cells?
To produce Abs that are specific for an Ag
What are the activated cytokines?
1) IL - 2
2) IL - 4
3) IL - 5
What is the function of IL - 2?
T-cell growth factor
What is the function of IL - 4?
B-cell growth factor
What is the function of IL - 5?
B-cells differentiation factor
What happens to activated B cells?
Activated B cells undergo clonal proliferation and differentiate to form plasma cells
What is the purpose of plasma cells?
To produce specific Igs
What are the major functions of Abs?
1) Neutralization of toxins and viruses
2) Opsonization (coating) of the pathogen, w/c aids its uptake by phagocytic cells
3) Complement activation
What are the 2 important functions of B cells?
1) Recognize Ags w/ their surface IgM that acts as an Ag receptor
2) Present epitopes to Th cells in association w/ class II MHC proteins
What are the factors affecting Ab production?
1) Genetic
2) Age
3) Nutritional status
4) Route of antigen
5) Dose of antigen
6) Multiple antigens
7) Adjuvants
What is the principle of how does genetic factor affect Ab production?
The response is controlled by immune response (Ir) gene located in the short arm of 6th chromosome
What gene controls the response in terms of Ab production?
Immune response (Ir) gene
Where is Ir gene located?
It is located in the short arm of 6th chromosome
What is the principle of how does age factor affect Ab production?
Full immunologic competence is achieved by about the age of 5 - 7 years for IgG, and 10 - 15 yrs for IgA by the development of lymphoid organs
What is the duration (or age) of achieving full immunologic competence for IgG (for age factor affecting Ab production)?
5 - 7 yrs
What is the duration (or age) of achieving full immunologic competence for IgA (for age factor affecting Ab production)?
10 - 15 yrs
What is the principle of how does nutritional status factor affect Ab production?
Deficiencies of amino acid and vitamins have shown to decrease the production of Abs
What are the components that causes decrease production of Abs (in terms of nutritional status affecting Ab production)?
Deficiencies of:
1) AA
2) Vitamins
What is the principle of how does route of Ag factor affect Ab production?
Parenteral administration of the Ag induces a better immune response than the oral or nasal routes
What type of route of transmission of Ag induces a better immune response (in terms of route of Ag affecting Ab production)?
Parenteral administration
What is the principle of how does dose of Ag factor affect Ab production?
1) A min. critical dose of Ag is essential to elicit an optimum immunological response
2) A very high or small dose fails to stimulate the immune system, a phenomenon is referred to as immunological paralysis
What is immunological paralysis?
It is a phenomenon that occurs where a very high or small dose of Ag fails to stimulate the immune system of an individual
What is the principle of how does multiple Ags factor affect Ab production?
Ab responses to 1 or more Ags may be diminished due to antigenic competition, or enhanced as seen after vaccination w/ triple vaccine (diphtheria, pertussis, tetanus), or may be similar
What is the triple vaccine (or 3 vaccines) that enhances Ab:Ag rxn (1:1 or more)?
1) Diphtheria
2) Pertussis
3) Tetanus
What are adjuvants?
These are substances that enhance the immunogenicity of an Ag
What are the purposes of adjuvants?
1) They delay the release of an Ag from the site of injection
2) They prolong the antigenic stimulus
What are the substances that are used as adjuvants?
1) Freund’s incomplete adjuvant
2) Freund’s complete adjuvant
3) Aluminum salts
4) Others, such as silica particles, beryllium sulfate, endotoxin, etc.
What is the characteristic of Freund’s incomplete adjuvant?
It is a protein Ag incorporated in H2O phase of H2O in oil emulsion
What is the characteristic of Freund’s complete adjuvant?
It is an incomplete adjuvant along w/ the suspension of killed tubercle bacilli
What bacteria is present (or incorporated) in Freund’s complete adjuvant?
Killed tubercle bacilli
What are the aluminum salts used as adjuvants?
1) Phosphate
2) Hydroxide
What are the primary tests used to detect humoral immunity?
The measurement of: 1) IgG 2) IgM 3) IgA present in the pt's serum
What are the methods for measuring Abs?
1) Radial immunodiffusion (Mancini method)
2) Immunoelectrophoresis
What is the principle of Mancini method (for measuring Abs)?
A single radial immunodiffusion assay used to determine the concentration of Ag in the sx
What are the principles of immunoelectrophoresis (for measuring Abs)?
1) Precipitation in agar under an electric field
2) It is the process of a combination of immuno-diffusion and electrophoresis
What is the meaning of CMI?
Cell-mediated immunity
What is CMI and what is its principle (when it comes to transfer)?
1) It is a specific type of acquired immune response not mediated by Abs but by sensitized T cells
2) This form of immunity is transferred from donor to recipient, not w/ antisera but w/ intact lymphocytes, hence, it is called cell-mediated immune reaction
What are the immunological functions of CMI?
1) It confers immunity in diseases caused by obligate intracellular bacteria
2) It participates in the immunological surveillance and immunity against cancer
3) It plays an important role in pathogenesis of delayed hypersensitivity reactions and in
4) pathogenesis of certain autoimmune diseases, such as autoimmune thyroiditis, encephalitis, etc.
Diseases caused by what type of bacteria are acted upon by immunological functions of CMI?
Diseases caused by obligate intracellular bacteria
What are the examples of bacteria that are acted upon by immunological functions of CMI?
1) Mycobacterium tuberculosis
2) Mycobacterium leprae
3) Brucella
True or False.
Viruses are also acted by immunological functions of CMI
True
If viruses are also acted by immunologic functions of CMI, what are the examples of diseases or infections brought by these viruses?
1) Small pox
2) Measles
3) Mumps
True or False.
Fungi are also acted by immunological functions of CMI
True
If fungi are also acted by immunologic functions of CMI, what are the examples of these fungi?
1) Histoplasma capsulatum
2) Blastomyces dermatitidis
3) Coccidioides immitis
True or False.
Parasites are also acted by immunological functions of CMI
True
If parasites are also acted by immunologic functions of CMI, what are the examples of these parasites?
1) Toxoplasma gondii
2) Leishmania donovani
What does T cells recognize and when is this recognized by T cells?
T cells recognize Ag only when presented to the surface of an APC by self MHC molecule
What is the cause of T cells recognizing Ag only when presented to the surface of an APC by self molecule?
This self MHC restriction results from (+) selection during maturation of T cells in the thymus
Where are MHC class I found?
These are found in all cells
Where are MHC class II found?
These are found on phagocytes
What is the action of clonal selection?
It increases the # of T cells
True or False.
Cell-mediated response is involved in harmful effects of hypersensitivity rxn included in transplant rejections, contact dermatitis, skin tests, and granuloma formation
True
T cells can recognize what?
T cell recognize specific Ags presented w/ MHC molecules on the surface of APCs
How many are the T cell receptors (TCR) of T cell in its surface?
Each T cell has 100,000 TCR
All of the TCR present in the surface of T cell recognizes what?
Recognizes 1 Ag (epitope)
What are the actions of activated T cells?
They start to proliferate, synthesize, and secrete IL-2, and express IL-2 receptors on cell surface
T cells differentiates to what?
To effector T cell and memory T cell populations
What is the life span of memory T cells?
They have long life span which is 20 - 30 yrs
What is the action of memory T cells?
They provide immunity when a person is re-exposed to same Ag
In cell mediated immunity, what are the events that happens during Ag presentation?
1) Formation of viral proteins by macrophage
2) Formation of Ag-MHC complex
In cell mediated immunity, what are the events that happens during Th cell activation?
1) Binding of Th cell to Ag-MHC complex
2) Release of cytokines from macrophage
3) Activation of Th cell to release cytokines
In cell mediated immunity, what are the events that happens during Tc cell (cytotoxic T cell?) activation?
1) Activation of virgin and memory Tc cells by cytokines
2) Promotion of mitosis and differentiation of Tc cells
In cell mediated immunity, what are the events that happens during cellular destruction?
1) Binding of effector Tc cell to infected body cell
2) Induction of cell lysis by release of perforins
What are the 2 classes of lymphocytes?
1) T lymphocytes or T cells
2) B lymphocytes or B cells
What is the component of lymphocytes?
Lymphocytes consist of heterogenous populations of cells that differ greatly from each other
What are the aspects where lymphocytes differ greatly from each other?
In terms of:
1) Origin
2) Lifespan
3) Preferred areas of settlement within the lymphoid organs
4) Surface structure
5) Function
Lymphocytes differentiate from what?
They differentiate from stem cells in the fetal liver, bone marrow, and thymus
Where do T cells develop and proliferate?
In the thymus
Where do B cells develop?
In the bone marrow
What are the characteristics of T lymphocytes?
1) They are the key players in adaptive immunity
2) Constitutes 65 - 80% of the circulating pool of small lymphocytes
3) Found in the inner subcortical regions but not in the germinal centers of the lymph nodes
4) Have a longer life span (months or yrs) than B lymphocytes
5) They are stimulated to divide on exposure to certain mitogens, such as phytohemagglutinin or concavalin A
6) Most human T cells have receptors for sheep RBCs on their surface and have the ability to form rosettes with them
What is the population of T lymphocytes?
65 - 80%
Where are T lymphocytes found?
Found in the inner subcortical regions but not in the germinal centers of the lymph nodes
Among the following, what lymphocyte has a longer life span?
a. T lymphocytes
b. B lymphocytes
a. T lymphocytes: these has a longer life span than B lymphocytes
How long is the life span of T lymphocytes?
Mos or yrs
What are the examples of mitogens?
1) phytohemagglutinin
2) concavalin A
What is the action of T lymphocytes in response to exposure to certain mitogens?
T lymphocytes divide on exposure to certain mitogens
Most human T cells have receptors for what cells and what is the resulting formation (if T cells come into contact w/ these type of cells)?
For sheep RBCs (has the ability to form rosette)
What are the 2 important groups of functions of T lymphocytes?
1) Regulation of immune responses
2) Effector functions
Since T lymphocytes regulates immune responses, what T lymphocyte is responsible for this action?
Helper (CD4) T cells / Th cells
The effector functions of T lymphocytes are mediated primarily by what T lymphocyte?
It is mediated primarily by cytotoxic (CD8) T cells / Tc cells
What are the actions of Tc cells?
Kills:
1) Allografts
2) Tumor cells
3) Virus-infected cells
What are the 2 major grps of T cells?
1) CD4 T cells
2) CD8 T cells
What is the component of mature T cells?
Either CD4 or CD8, but never both
What is the approximate ratio of CD4 and CD8 T cells in normal human peripheral blood?
2:1
What are the characteristics of CD4 T cells?
1) Constitutes about 65% of peripheral T cells and are found mainly in the thymic medulla, tonsils, and blood
2) CD4 displayed on the surfaces of these T cells recognize a nonpeptide-binding portion of MHC class II molecules
3) CD4 are restricted to the recognition of pMHC (or MHC?) class II complexes
4) They are involved in the induction and regulation of immune responses
What is the population of CD4 T cells?
About 65%
Where are CD4 T cells primarily found?
1) Thymic medulla
2) Tonsils
3) Blood
Where is CD4 located in T cells?
In the surface of T cells
What is the action of CD4 present in T cells?
It recognizes a nonpeptide-binding portion of MHC class II molecules
CD4 are restricted to what?
To the recognition of pMHC (or MHC?) class II complexes
What MHC class recognizes CD4?
MHC class II complexes
What are the main functions of helper T cells?
1) Help B cells to be transformed into plasma cells
2) Help CD8 T cells to become activated Tc cells
3) Help macrophages to mediate delayed type hypersensitivity rxns
4) Help in the Ag-specific activation of B cells and effector T cells
What is the action of Th-1 cytokines?
To activate cytotoxic inflammatory and delayed hypersensitivity rxns
What are the actions of Th-2 cytokines?
1) Help in the production of ILs w/c encourage production of Abs especially IgE
2) Associated w/ regulation of strong Ab and allergic responses
What are the 2 subpopulations of CD4 T cells?
1) Th-1 cells
2) Th-2 cells
What are the actions of Th-1 cells?
1) Activate Tc cells by producing IL-2
2) Help in the development of hypersensitivity responses by producing primarily IL-2 and gamma interferon
What is needed by Th-1 cells to activate Tc cells?
IL-2 (w/c is produced by Th-1 cells)
How do Th-1 cells help in the development of hypersensitivity responses?
By producing primarily IL-2 and gamma interferon
What are the actions of Th-2 cells?
1) Perform B cell helper function by producing primarily IL-4 and IL-5
2) Associated w/ regulation of strong Ab and allergic responses
How do Th-2 cells perform B cell helper function?
By producing primarily IL-4 and IL-5
What is the action of gamma interferon and IL-12?
To regulate the balance bet Th-1 and Th-2 cells
What are the characteristics of CD8 T cells?
1) Also known as cytotoxic T (Tc) and suppressor T (Ts) cells
2) They account for approx 1/3 of all mature CD3 cells
3) Found mainly in the human bone marrow and gut lymphoid tissue
4) Perform mainly cytotoxic functions
What is the population of CD8 T cells?
Approx 1/3 of all mature CD3 cells
Where are CD8 T cells mainly found?
In the human bone marrow and gut lymphoid tissue
What are the cytotoxic functions performed by CD8 T cells?
To kill:
1) Virus-infected cells
2) Allograft cells
3) Tumor cells
What process is T cell mediated cytotoxicity?
It is an apoptotic process
What are the 2 pathways of T cell mediated cytotoxicity?
1) Granzyme-induced apoptosis (Ca2 dependent)
2) Ca2 independent
What is the principle (or action) of granzyme-induced apoptosis (as pathway of T cell mediated cytotoxicity)?
Involves the release of proteins known as perforins w/c insert themselves in the target cell membranes forming channels that allow the diffusion of enzymes (granzymes, w/c are serine esterases) into the cytoplasm
What are perforins and what is their action?
They are proteins that are released and after being released, they insert themselves in the target cell membranes forming channels that allow diffusion of enzymes into the cytoplasm
What is the principle (or action) of Ca2 independent pathway (as pathway of T cell mediated cytotoxicity)?
It depends on signals delivered by the Tc cell to the target cell, w/c require cell-to-cell contact
What are the 2 signals that activate T cells?
1) The interaction of the Ag and the MHC protein w/ the T cell receptor specific Ag
2) A costimulatory signal
What is also necessary for efficient Th cell activation?
IL-1 secreted by the macrophages
What is most crucial in producing a Th cell that is capable of performing their regulatory, effector, and memory functions?
IL-2 produced by Th cells
What are the characteristics of T cell receptor (TCR)?
1) It consists of 2 polypeptides
2) Each T cell has a unique TCR on its surface, thereby implying that hundreds of millions of different T cells occur in each person
What are the 2 polypeptides that comprises TCR?
1) Alpha
2) Beta
The 2 polypeptides that comprises TCR are associated w/ what?
Associated w/ CD3 proteins
What is the action of activated T cells and activated B cells?
Both produce a large # of cells specific for those Ags
How do T cells differ from Igs?
1) T cells have 2 chains rather than 4 chains in Igs
2) T cells recognize Ag only in conjunction w/ MHC proteins, whereas Igs recognize free Ags
What are the 3 regions of both B cell receptor and T cell receptor?
1) Variable regions
2) Constant regions
3) Transmembrane region
What are the 2 chains that comprises B cell receptor?
1) Light chain
2) Heavy chain
What are the 2 chains that comprises T cell receptor?
1) Alpha chain
2) Beta chain
What are the actions of superantigens?
1) To activate a large # of Th cells unlike Ags w/c activate 1 or a few Th cells
2) Play a very important role in pathogenesis of Staphylococcal TSS caused by S. aureus
What are the examples of superAgs?
Certain proteins such as:
1) Staphylococcal enterotoxins
2) TSS toxins
3) Certain viral proteins
What is the result of activation of T cells?
It results in release of IL-2
Where does IL-2 (being released as a result of activation of T cells) come from?
From the T cells and tumor necrosis factor (TNF) from macrophages
What are the characteristics of memory T cells?
1) Confer host immunity w/ the ability to respond rapidly and vigorously for many yrs after the initial exposure to a microbe or other foreign mats
2) Live for many yrs or have the capability to reproduce them
3) A large # of memory cells are produced, hence, 2ndary response is enhanced and is greater than primary response
4) Activated by small quantity of Ags and require less co-stimulation than do the naive and unactivated T cells
5) Activated memory cells produce greater amts of ILs than do naive cells when they are 1st activated
What are the effector functions of T cells?
1) Cytotoxicity
2) Delayed hypersensitivity
What are the actions (or importance) of cytotoxicity?
1) Required primarily to destroy virus-infected cells and tumor cells
2) Also plays an important role in graft rejection
How is cytotoxicity activated?
1) Inserting perforins and granzymes (degrading enzymes) into the infected cell
2) By the Fas-Fas ligand (FasL) interaction
3) By Ab-dependent cellular cytotoxicity (ADCC mechanism)
How does Tc cells kill virus-infected cells?
By the FasL interaction
What is FasL and what is the principle of action of FasL?
It is a protein expressed on the surface of many cells. When a cytotoxic TCR recognizes an epitope on the surface of virus infected cells, FasL appears on the Tc cells
How do target cells achieved apoptosis?
When Fas and FasL interact
What is the action of NK cells (in terms of cytotoxicity)?
NK cells also kill target cells by FasL interaction
What is immune surveillance?
It is a phenomenon where Tc cells kill the tumor cells
Where does new Ags usually develop?
On surface of many tumor cells
New Ags present on the surface of tumor cells are bound to what?
These Ags are bound to class I proteins
What action happens to Ags (on surface of tumor cells) that are bound to class I proteins?
They are recognized by Tc cells w/c are activated to proliferate IL-2
What is the action of resultant clone of Tc cells?
It can kill the tumor cells
For the function of Tc cells playing an important role in graft rejection, what is the principle in this function?
Cytotoxic CD8 cells recognize the class I MHC molecules on the surface of the foreign cells. Helper CD4 cells recognize the foreign class II molecules on certain cells, such macrophages and lymphocytes in the graft. The activated helper cells secrete IL-2 w/c stimulates the Tc cells to produce a clone of cells w/c kills the cells in the allograft
What is the action of CD4 cell, Th-1 subset cells, and macrophages (in terms of delayed hypersensitivity)?
These mediates the delayed hypersensitivity rxns against Ags of many intracellular pathogens
What are the substances (or ILs) that are produced by CD4 cells and what is the function of these substances being secreted?
CD4 cells produces ILs such as:
1) Gamma interferon
2) Macrophage activation factor
3) Macrophage inhibition factor
These ILs mediate delayed hypersensitivity rxns
What substance (or IL) is produced by Th-1 cells and what is the action of this IL?
Th-1 cells produces IL-12-gamma interferon w/c activates macrophages and thereby enhances the ability of the macrophages to kill M. tuberculosis
What is the important role of gamma interferon?
It plays an important role to control infections caused by M. tuberculosis, Listeria monocytogenes, and other intracellular microbes
What is the life history of T lymphocytes?
1) Precursors mature in the thymus
2) Naive CD4+ and CD8+ T cells enter the circulation
3) Naive T cells circulate through lymph nodes and find Ags
4) Clonal expansion; differentiation into effector and memory cells
5) Effector T cells migrate to sites of infection
6) Eradication of infection
