Immunology 1: Lymphoid Cells/Tissue Flashcards
What is plasma?
the components of blood after red and white blood cells have been removed; contains clotting factors, antibodies, complement proteins, etc.
What is serum?
the components of blood that are neither cells nor clotting factors
What is a titer?
the measurement of the concentration of a substance in a solution; most typically refers to the concentration of antibodies specific for a particular antigen
What does the suffix -penia mean?
deficiency, or a lack of
What are bands?
immature neutrophils that are observed during bacterial infections
What are the recognition mechanisms of the innate immune system? (re: onset, response type, number of specificities, activity over time)
rapid response (hours); fixed specificities; limited number of specificities; constant response during course of infection; same reponse for each encounter with a specific pathogen
What are the recognition mechanisms of the adaptive immune system? (re: onset, response type, number of specificities, activity over time)
slow response (days to weeks); variable response; lymphocytes have numerous highly selective specificities; improves during response; involves clonal expansion and memory of response for increased effectiveness in future encounters
What are pattern recognition receptors (PRRs)?
receptors expressed on the surfaces of innate immune cells that recognize pathogen-associated molecular patterns (PAMPs); this concept is the reason for limited specificities of the innate immune response
How do cells of the acquired immune system have numerous specificities?
the B and T cells express highly specific receptors that recognize specific structures of a particular pathogen
What are the three broad categories of the non-cellular innate immune response?
mechanical/chemical; microbiological; complement cascades
Name examples of innate immunity mechanical barriers.
epithelial cells joined by tight junctions; longitudinal flow of air/fluid; movement of mucus by cilia
Name examples of innate immunity chemical barriers.
fatty acids; low pH; enzymes; saliva; defensins (antibacterial peptides)
Name examples of innate immunity microbiological barriers.
normal flora of skin, GI tract, respiratory tract, UG tract, eyes
When the complement cascade is initiated, there are three end products that help to control or eliminate infectious agents. They are:
- anaphylotoxins: inflammatory mediators
- opsonins: mark pathogens for uptake & destruction by neutrophils/macrophages
- membrane attack complex: inserts into bacterial outer envelopes to perforate/kill pathogenic cells
What are the three broad categories of the cellular innate immune response?
immune cells
What are the primary lymphoid tissues?
bone marrow and thymus
In what tissue/organ are all acquired immune responses initiated?
secondary lymphoid tissue, such as spleen, Peyer’s patches, lymph nodes, tonsils, and mucosa-associated lymphoid tissue (MALT)
What are the functions of erythrocytes?
- transport of oxygen to all cells in the body
2. clearance of immune complexes from circulation
What are the functions of megakaryocytes?
produce platelets, or thrombocytes
What are the functions of bands?
during bacterial infections they move in large numbers to take up and kill bacteria
What are the functions of neutrophils?
- recognize pathogens by their PRRs
2. control bacterial and fungal infections
What is a monocyte?
monocytes are circulating precursors to macrophages; they leave the vasculature, move into tissues, and become mature machrophages
What are the innate immune functions of a macrophage?
recognize (by PRRs), engulf, and destroy potential pathogens
What are the acquired immune functions of a macrophage?
1 of 3 professional antigen presenting cell types that can activate T cells; express antibody Fc receptors that allow it to be bridged into an acquired immune response
What are the functions of eosinophils?
primary role is to control parasite infections; have IgE antibody receptors; contain granules with inflammatory mediators and other compounds that are toxic to parasites
What are the functions of basophils?
primary role is to control parasite infections; appear to function very similarly to eosinophils, otherwise they are poorly characterized cells
What cell types of the innate immune system are considered granulocytes?
neutrophils, bands, eosinophils, basophils
What are the functions of mast cells?
primary role is to control parasite infections; granules contain inflammatory mediators (including histamine); have high affinity IgE receptors on surface
What are the functions of natural killer cells?
innate control of viral infections; bear no antigen-specific receptor therefore are a purely innate cell; identify and kill infected cells to limit the replicating cycle of the pathogen; express Fc receptors, therefore they are the effectors of antibody-dependent cell mediated cytotoxicity (ADCC)
Inflammation is important to the innate control of infections, and it’s critical for the initiation of the adaptive immune response because…
…it promotes movement of antigens and antigen-presenting cells into the nearest secondary lymphoid tissues, where the adaptive immune response can be initiated.
The spleen is a secondary lymphoid tissue important for:
filtering blood for phagocytes to remove pathogens; also for storing new RBCs and removing old RBCs (red pulp)
Lymph nodes are dispersed throughout the body, connected by _____, and capture antigens from _____.
lymphatic vessels; lymph
____ are the most organized tissue of the GALT, or gut-associated lymphoid tissue.
Peyer’s patches
Describe the basic organization of secondary lymphoid tissue, such as that seen in white pulp/Peyer’s patches/lymph nodes.
germinal center within B cell zone, closely associated concentrated T cell zone occupied by antigen presenting cells; T cell interacts more closely with blood in order to recognize the antigen and supply a second signal to activate the B cells
What is the location and function of microfold cells (aka M cells)?
located in Peyer’s patches; role is to sample antigens from gut lumen, transport into patch for antigen presentation to T cells and sampling by B cell receptors
How do antigens and antigen presenting cells get transported from Peyer’s patches to lymph nodes?
via the efferent lymphatics of the Peyer’s patch
What 3 cell types have the role of antigen presentation to T cells?
dendritic cells (innate cell) macrophages (innate cell) B cells (adaptive cell)
What is the function of dendritic cells?
most potent antigen-presenting cells; high surface areas for interacting with many T cells at once; not good killer cells
What are the antigen-presenting functions of macrophages?
activation of adaptive immune response; recognition and removal of bacterial and fungal pathogens
Two types of lymphocytes are:
B cells and T cells
Production and secretion of antigen-specific antibodies is the role of which lymphocyte?
B cells
Which lymphocyte has cytotoxic and helper functions?
T cells
Effector CD4+ cells do what?
modulate activity of other immune cell types through cytokine production
Effector CD8+ cells do what?
recognize and kill infected host cells
Why are there two “arms” of the acquired immune response?
for clearing two types of pathogens from the host: those that reside in extracellular spaces, and those that reside within cells
Antibodies are best for clearing ____ infections and T cells response is best for clearing ___ infections.
extracellular; intracellular
What is somatic recombination?
mechanism that allows for generation of diverse lymphocyte receptors for specific antigen recognition; at the DNA level a cassette system is used to rearrange genes that code for antigen receptors
What are the two forms of antigen-specific receptors utilized by lymphocytes?
- antibodies from B cells
- T cell receptors
(together these are immunoglobulins)
When binding antigens, B cell receptors recognize __?__, and T cell receptors recognize __?__.
almost any antigen; peptides only
What is an MHC molecule?
major histocompatability complex molecules; this is the protein that presents the antigenic peptide to T cells for recognition
What is the difference between the two classes of MHC molecules?
LOCATION: class I = found on all nucleated cells class II = found only on antigen-presenting cells
Myeloid Progenitor cells are the precursors for:
Granulocytes, macrophages, dendritic cells, and mast cells
Another name for granulocytes is:
Polymorphonuclear cells (PMNs)
Name a WBC type that functions to kill antibody-coated parasites.
Eosinophils
What WBCs have an unknown function but probably do something similarly to eosinophils?
Basophils
What are the immature, circulating precursors to macrophages?
Monocytes
Which cells are the most potent stimulators of T Cell responses?
Dendritic cells
These cells take up antigen at the site of infection and present the antigens to naive T cells in secondary lymphoid tissues.
Dendritic cells
The common lymphoid progenitor gives rise to these three types of cells:
T cells and B cells (specific). Also NK cells (Non-specific)
This type of cell is found in the corona of the PALS within white pulp of the spleen:
B cells
These cells are recycled in the red pulp (cords of biliroth) of the spleen:
RBCs
Within the lymph nodes, _______ cells are localized in follicles, with _______ cells distributed more diffusely in paracortical areas.
B cells; T cells
Germinal centers are _____ cell follicles in which ____ cells are undergoing intense proliferation following antigenic stimulation with T cell help.
B cell; B cell
Give 4 examples of gut associated lymphatic tissue (GALT)
Tonsils, adenoids, appendix and Peyer’s patches
Bronchial-associated lymphoid tissue (BALT) and mucosal-associated lymphoid tissue (MALT) are similar to GALT, but are more diffusely organized lymphoid tissues that protect:
The respiratory epithelium
Inflammatory mediators (cytokines) facilitate uptake of _______ by phagocytes and increase the flow of ______ toward the draining lymphoid tissue. (Facilitates antigen transport to secondary lymphoid tissue)
Antigen; lymph
The ability of lymphocytes to produce different receptor molecules; therefore each potentially binding to a different specific component of an infectious agent, is referred to as:
The lymphocyte repertoire
The body’s ability to selectively remove (most) lymphocytes that bear receptors that bind to “self” antigens, thus preventing the immune system from attacking host tissues is referred to as:
Self tolerance
Briefly describe clonal selection.
Central principle of adaptive immunity; when a lymphocyte is stimulated by binding of its receptor to its cognate antigen, lymphocyte proliferates, gives rise to clones that bear identical antigen-receptor specificity
What cell types will function in protection against parasites?
eosinophils, basophils, mast cells
What cell types will function in protection against viruses?
natural killer (NK) cells
What cell types will function in protection against fungus?
neutrophils
What cell types will function in protection against bacteria?
macrophages, neutrophils
What is the lymphatic system and what is its function?
collects material from EC fluid and filters it through lymph nodes, then returns it to the blood circulation; edema “flushes the bad stuff toward the sewer” (lymphatic system)
Random recombination of immunoglobulin genes that generate complete coding regions for the antigen-binding portions of the lymphocyte receptor molecules is referred to as:
Somatic recombination
Name the three antigen presenting cell types:
Macrophages, dendritic cells, B cells
True of false: MHC class I/II molecules bind very tightly to many different peptides in a very specific way.
False. They bind tightly in a non-specific way
True or false: the T cell binds most favorably to peptides that are presented on MHC molecules.
False. The T cell ONLY binds to peptides that are presented on MHC molecules
Name the 3 effects of antibodies.
Neutralization
Opsonization
Complement activation
Briefly describe antibody mediated neutralization
Abs can neutralize some pathogen-derived toxins, and even some pathogens
Briefly describe the opsonization function of antibodies.
Some Abs can coat antigens (or pathogens) which facilitates uptake of the antigen by phagocytes or NK cells
Briefly describe the complement activation function of antibodies.
Some types if antibodies, when bound to specific antigen (pathogen), serve as a receptor for uptake or destruction of the antigen (pathogen)
In antibody-dependent cell-mediated cytotoxicity (ADCC), antibodies activate ______ cells.
NK cells
Name the two primary populations of T cells.
CD8 and CD4 cells
CD8 cells recognize peptide antigen present on MHC class _____ molecules.
MHC class I
CD4 cells recognize antigen peptides on MHC class _____ molecules.
MHC class II
Armed (activated) effector CD8 cells are programmed for only one purpose:
To kill cells that have the cognate peptide, MHC class I complex on their surface. Thus they are also called cytotoxic T lymphocytes or killer T cells. So they are like contract killers with a specific target.
If any nucleated cell of the body is host to an intracellular pathogen, this class of cells will find them and kill them.
Armed effector CD8 (Killer) T cells
This class of lymphocyte, once it encounters its cognate peptide MHC II and receives proper costimulation (from the antigen presenting cell), will proliferate and differentiate into armed effector T cells that secrete cytokines which modulate the activity of other immune cells. Also called helper T cells.
CD4 T cells
The primary role of these cells is supply cytokine signals to macrophages; these signals upregulate various activities of the macrophage which increase its ability to kill ingested bacteria and to more efficiently present peptide antigens.
T helper 1 CD4 cells aka TH1 CD4 cells
These cells secrete cytokines that stimulate B cells to produce Abs that are effective for opsonizing pathogens.
TH1 CD4 cells
In general, TH1 CD4 cells help stimulate immune responses that are most efficient for destroying intracellular or extracellular pathogens?
intracellular
The primary role of this subgroup of lymphocytes is to promote Ab-mediated immune responses.
T Helper 2 CD4 cells aka TH2 CD4 cells
TH2 CD4 cells supply cytokine signals that stimulate B cells to produce antibodies that best participate in processes that:
Eliminate extracellular pathogens (such as neutralization and complement fixation)
