Specific Immunity Flashcards
Categories of Specific Immunities
natural v artificial, passive v active
natural
what you find in nature; 250 years and below
artificial
what you find in a hospital
passive
give someone antibodies
characteristics of passive
Works immediately but does not last long and helps immune system (3-6 months)
Natural passive
breast milk
artificial passive
acquiring antibodies in hospital (immunotherapy)
Colostrum
antibodies in breastmilk
active
when immune system is stimulated by an antigen
what must you have for active immunity to work
Must have immunocompetency
Immunocompetency
immune system is healthy; takes longer (2 weeks)
natural active
getting sick
artificial active
vaccine
human Leukocyte Antigens (HLAs)
important in Self-recognition by the immune system and Tissue compatibility (organ donation)
Major Histocompatibility Complexes are a group of (MHCs/HLAs)
group of cell surface receptors
3 classes of MHCs
MHC class 1,2,3
MHC Class I
self recognition
location of MHC Class I
surface of virtually all nucleated cells (except red blood cells)
function of MHC Class I
determine recognition of “self” molecules and cells.
absence of MHC class I molecules
triggering an immune response
MHC Class II
Foreign Antigen Presentation
location of MHC Class II
surface of macrophages, dendritic cells, and B cells (white blood cells)
function of MHC Class II
React with foreign antigens and present them to T cells
MHC Class III
Encode secreted complement components
B Cell Lymphocyte Receptors Antigen Binding
bind to free floating antigens
B Cell Lymphocyte Receptors structure
Y-shaped protein; two heavy chains and two light chains (four polypeptide chains)
Fc Region
constant region that binds to B cells and triggers activation.
Gene Regions of Immunoglobulins
Heavy chain genes have V, D, J, and C regions; light chain genes have V, J, and C regions
Variability
The V and D regions (in heavy chains) are responsible for the vast diversity of antigen-binding sites.
Immunoglobulin mechanism
Each B cell randomly selects one gene from each region during development producing only one type of antibody
Constant Region (C)
determines the antibody’s class (e.g., IgG, IgM) and its function
T Cell Lymphocyte Receptors binding
Bind only to processed antigens
structure T Cell Lymphocyte Receptors
Structurally different from B cell receptors
T-Cell Receptors vs. B-Cell Receptors
T-cell lymphocyte receptor (TCR) which binds to antigens are secreted, TCRs are smaller than immunoglobulins, TCRs are always membrane bound while immunoglobulins are membrane bound/secreted into blood plasma, TCR one binding site and immunoglobulin 2 binding sites
The Clonal Selection Theory
explains how the immune system can recognize millions of different antigens without attacking the body’s own cells
stages of clonal selection theory
- Proliferative Stage (Fetal Development)
- Clonal Deletion Stage (Fetal Development):
- Clonal Selection and Expansion Stage (Post-Birth):
Proliferative Stage (Fetal Development)
Millions of different B cells are generated during fetal development. Each B cell randomly selects specific V, D, J, and C genes to create a unique immunoglobulin; occurs in fetal bone marrow
Clonal Deletion Stage (Fetal Development)
B cells producing antibodies that recognize self-antigens (molecules in fetal tissue) are eliminated through apoptosis (programmed cell death). This process ensures that only B cells recognizing non-self antigens survive.
Clonal Selection and Expansion Stage (Post-Birth)
After birth, if a B cell encounters an antigen that its antibody recognizes, it is stimulated to proliferate (clone itself) and produce large quantities of its specific antibody. These antibodies are secreted into the blood plasma to target the foreign antigen.
T cell maturation
Produced in the bone marrow, but mature in the thymus. Different types of T cells exist, classified by their CD markers (e.g., CD4 helper T cells, CD8 cytotoxic T cells). Both migrate throughout the body via the bloodstream and lymphatic system.
B cell maturation
Produced and mature in the bone marrow, then released into circulation.
Antigens
provoke an immune response by binding to antibodies or T-cell receptors
common antigen types
Proteins (most common), Lipoproteins, Glycoproteins, Nucleoproteins,
Some polysaccharides
antigen characteristics
Smaller antigens are less effective, Larger, more complex antigens are more immunogenic
Epitopes
specific regions on an antigen where antibodies bind
antigen types
Haptens, Autoantigens, Alloantigens, Superantigens, Allergens
Haptens
requires large carrier molecule to stimulate immune response
Autoantigens
Antigens from your own body. These are problematic as they trigger autoimmune diseases. They often originate from immune-privileged sites (e.g., eye, thyroid, testes) that are shielded from the immune system during fetal development.
Alloantigens
Antigens from other organisms of the same species. These are encountered during organ transplantation.
Superantigens
Potent antigens (from bacteria and viruses) that over-activate T cells, leading to excessive cytokine release and potentially causing significant tissue damage, toxic shock syndrome, multi-organ failure, and autoimmune diseases.
Allergens
Antigens from non-pathogenic sources (e.g., pollen, pet dander) that trigger allergic reactions.
Antigen-presenting cells (APCs)
crucial for initiating an adaptive immune response
key APCs
Macrophages
Dendritic cells
B cells
APC process
- engulfing 2. processing 3. presentation 4. T cell activation
Engulfment
APCs engulf antigens through phagocytosis.
Processing
Antigens are broken down and modified to enhance immunogenicity
Presentation
Processed antigens are loaded onto Major Histocompatibility Complex (MHC) molecules (MHC class I or MHC class II) and displayed on the APC’s surface
T Cell Activation
The APC presents the antigen to T cells, specifically helper T cells (via MHC class II and CD4 interaction). The APC searches for the specific helper T cell with a T cell receptor that recognizes the presented antigen.
importance of APC process
vital for initiating a targeted immune response against specific pathogens; ensures only the appropriate T cells are activated.
(APCs) and Helper T Cells
Dendritic cells, phagocytosis, Antigen Presentation, Interleukin-12 (IL-12), Interleukin-2 (IL-2)
Phagocytosis
Dendritic cells engulf the invader, forming a phagosome which fuses with a lysosome (phagolysosome). The invader is destroyed.
Antigen Presentation
dendritic cell processes foreign molecules and presents them to matching helper t cell
Interleukin-12 (IL-12)
Once the correct helper T cell is found, the APC releases IL-12, signaling “You’re the one!”
Interleukin-2 (IL-2)
helper T cell confirms it received the message and will activate the specific immune response
Once activated, the helper T cell
Divides and Stimulates other cells
divides
Creating various helper T cell lines, including memory helper T cells (for future infections) and T regulatory cells (which we’ll discuss later).
stimulates other cells
Including B cells. Helper T cells act as coordinators, directing the immune response.
what are b cells primarily activated by
helper T cells or free-floating antigens
Helper T cell activation
primary method of B cell activation. The helper T cell signals the B cell to begin working.
Independent B cell activation
B cell lymphocytes can float freely and bind to free-floating antigens without needing helper T cell activation.
Once activated, B cells:
divide, produce plasma b cells, then produce memory b cells
b cell activation divide
Producing plasma B cells and memory B cells.
b cell activation plasma b cells
Produce large amounts of antibodies (immunoglobulins) of various types. These cells and their antibodies exist for only a few months.
b cell activation memory b cells
Divide slowly, producing fewer antibodies. They are crucial for a faster response to future encounters with the same antigen.
antibody functions
Complement fixation, Opsonization, Neutralization, Agglutination and precipitation
Complement fixation
Enhances the complement system, leading to more efficient pathogen destruction
Opsonization
Coats target cells, enhancing phagocytosis.
Neutralization
Covers viral particles or toxins, preventing them from binding to host cells.
Agglutination and precipitation
Clumps cells or molecules together, rendering them inactive.
Monoclonal Antibodies
target particular cells or molecules; used in research, diagnostics (like pregnancy tests), and therapeutics (treating conditions like coronavirus and cancer).
T cells are activated by
only by antigen-presenting cells
CD8+ T cells (Cytotoxic T cells)
cells directly kill infected, cancerous, or foreign cells
what do CD8+ T cells (Cytotoxic T cells) release
perforins and granzymes
perforins
create holes in target cell membranes
granzymes
induce apoptosis – programmed cell death
CD4+ T cells (Helper T cells)
coordinate the immune response by activating other immune cells
types of CD4+ T cells (Helper T cells)
Th1, Th2, Th17, Tregs
Th1
Activated by dendritic cells and interleukin-12 (IL-12). Involved in delayed hypersensitivity (e.g., poison ivy reaction)
Th2
Activated by other interleukins and APCs. Activate B cells and contribute to humoral immunity.
Th17
Promote inflammation.
Tregs
Suppress immune responses, preventing autoimmunity and excessive inflammation. They maintain tolerance to self-antigens and commensal microbiota.
Natural Killer (NK) cells
Lack antigen specificity; part of the innate immune system. Kill infected or cancerous cells.
Natural Killer T (NKT) cells
Recognize lipid antigens; produce cytokines, granzymes, and perforins.
passive immunization
Immunotherapy involves providing a patient with pre-formed antibodie
immunotherapy antibodies characteristics
molecules that cannot replicate; their effectiveness lasts only as long as the molecules remain intact and active in the body—typically a few months. The immediate benefit is their rapid action.
types of immunotherapy
immune Serum Globulin (ISG), Specific Immune Globulin (SIG), Monoclonal Antibodies, Animal-Derived Antisera
Immune Serum Globulin (ISG)
support immune-deficient patients or provide antibodies when the body cannot produce them efficiently. It’s effective against various diseases, including measles and Hepatitis A.
Specific Immune Globulin (SIG)
contains high titers of antibodies specific to that infection; derived from the serum of individuals recovering (convalescent) from a specific infection, such as tetanus, chickenpox, pertussis, or Hepatitis B
Monoclonal Antibodies
single type of antibody highly specific to a particular infectious disease
Animal-Derived Antisera
Used when human immunoglobulin is unavailable, particularly for potent toxins like diphtheria, botulinum toxin, and snake or spider venom. These are often derived from horses, which are injected with inactivated toxins to produce antisera. However, these can cause allergic reactions.
goal of vaccine
teach the immune system to recognize and fight a pathogen without causing the disease itself.
Weakened (attenuated) pathogen vaccines
Use a live but weakened version of the pathogen.
Inactivated pathogen vaccines
Use a killed version of the pathogen
Subunit, recombinant, polysaccharide, and conjugate vaccines
Use specific components of the pathogen (e.g., proteins, sugars) rather than the whole pathogen.
three most common vaccine design mechanisms
killed/inactivated viruses, live attenuated viruses, and vaccines from microbial parts
Killed/Inactivated Viruses
use whole pathogens that have been killed in a lab setting, preserving their antigens; Common methods for inactivation include radiation, chemicals, or heat
example of killed/inactivated viruses
Hepatitis A vaccine, flu shot (inactivated), Salk polio vaccine, rabies vaccine
advantages of killed/inactivated viruses
No risk of causing the disease,Safe for individuals with compromised immune systems, Doesn’t require special storage conditions
disadvantages of killed/inactivated viruses
Requires a larger dose or booster shots because the antigens aren’t self-replicating, Growing pathogens in a lab (often requiring BSL-2, BSL-3, or even BSL-4 facilities) can be costly and risky.
mechanisms Live Attenuated Viruses
weakened, live versions of the pathogen; they are alive but have reduced virulence
example of live attenuated viruses
MMR vaccine (measles, mumps, rubella), smallpox vaccine (weakened version), Sabin oral polio vaccine, chickenpox vaccine, yellow fever vaccine, nasal flu spray.
advantages live attenuated viruses
Easy to grow in a lab, requiring less stringent safety measures, usually requires a smaller dose because the attenuated virus can replicate within the body amplifying the immune response,
Can provide longer-lasting immunity.
disadvantages live attenuated viruses
Potential for transmission to others (though this can also be beneficial for herd immunity).
Risk of causing disease in immunocompromised individuals.
Requires special storage to maintain the viability of the attenuated pathogen.
Risk of reversion to wild-type virulence, especially with single-point mutations.
Vaccines from Microbial Parts/subunit vaccine mechanisms
use only the antigenic determinants (epitopes) of the pathogen, not the whole pathogen. This requires identifying the specific antigens responsible for triggering an immune response.
examples of subunit vaccines
HPV vaccine, shingles vaccine, DTaP (diphtheria, tetanus, pertussis) vaccine, Tdap (adult version of DTaP).
advantages of subunit vaccine
Easy to grow and produce in labs.
Generally don’t require special storage.
Very safe, as they don’t contain any live components of the pathogen.
disadvantages of subunit vaccine
Requires extensive research to identify the relevant antigens.
May require multiple doses or adjuvants (substances that enhance the immune response) to achieve effective immunity.
recombinant vaccines mechanisms
use genetically engineered microbes or antigens
examples of recombinant vaccines
hepatitis B vaccine, mRNA vaccines
advantages of recombinant vaccines
can be produced in large quantities, highly specific and safe
disadvantages of recombinant vaccines
requires advanced genetic engineering techniques, can be expensive
vaccine administeration
injection, nasal spray, oral
Adjuvants
compounds that enhance immunogenicity by prolonging antigen retention in the bloodstream or tissues
common vaccine side effects
local and systemic reactions
local reactions
Redness, swelling, and aching at the injection site (inflammatory response) around 1 day
systemic reactions
Fever (systemic response to the antigen). This is a desired effect, indicating the immune system is actively responding.
rare vaccine side effects
Bowel Obstruction, febrile seizures
