Term
| Where do lymphocytes come from? |
|
Definition
| stem cells in the bone barrow |
|
|
Term
| What are the two types of lymphocytes? |
|
Definition
T cells
-thymus dependent
B Cells
-bursa (bone marrow) |
|
|
Term
| What are the central lymphoid tissues? |
|
Definition
|
|
Term
| What are the peripheral lymphoid tissues? |
|
Definition
lymph nodes
spleen
tonsils
gut-associated lymphoid tissue |
|
|
Term
|
Definition
|
|
Term
True or False
The thymus develops as mammals age |
|
Definition
|
|
Term
| How can you differentiate T cells & B cells? |
|
Definition
| -presence of antigens using specific antibodies |
|
|
Term
| What characterizes B-cells? |
|
Definition
| presence of a B-cell antibody-receptor complex |
|
|
Term
| What happens when antibodies come in contact with antigens? |
|
Definition
1. B cells proliferate (clonal expansion)
2. Differentiate into Plasma Cells & Memory Cells |
|
|
Term
| What are plasma cells? What is their appearance? |
|
Definition
B cells which secrete antibody (immunoglobulin) specific to a particular antigen
-nucleus is off center, cartwheel chromatin pattern, obvious Golgi apparatus |
|
|
Term
|
Definition
| B cells which have a long lifespan, will provide a 'residual' population to invoke a rapid immune response if the antigen in question is encountered in the future |
|
|
Term
| How do T cells interact with antigens? |
|
Definition
| interacts with fragments of antigens expressed on the surface of cells that have digested a pathogen or are expressing an antigen abnormally |
|
|
Term
| What happens after T cells interact with antigens? |
|
Definition
| Proliferation (Clonal Expansion) & differentiation into CD4+ or CD8+ |
|
|
Term
|
Definition
'helper' cells
-secrete cytokines which upregulate the immune response |
|
|
Term
| What are the different types of helper cells? |
|
Definition
Th3-Cell Response
Th2-Cell Response |
|
|
Term
|
Definition
-release Interferon-gamma IFN-Y
-activate macrophages & B cells
-trigger B cells to secrete antibodies |
|
|
Term
|
Definition
| Release interleukins to activate mast cells & eosinophils |
|
|
Term
| What does the 'CD' mean in CD-4 & CD-8 cells? |
|
Definition
Cluster Designation
-antigens on the surface of T cellsm |
|
|
Term
| What is the 'normal' ration of CD4+ to CD8+ cells? How does this change in AIDS? |
|
Definition
2:1
greatly reduced in patients with AIDS |
|
|
Term
|
Definition
cytotoxic T-cells which directly kill virus-infected cells/tumour cells
*lesser effect of cytokine release |
|
|
Term
| What are the 3 important functions of activated T cells in the immune system? |
|
Definition
1. Cell-mediated immunity (killing recognized cells)
2. Helper roles (cytokines to help activate B ell synthesis of antibodies)
3. Delayed hypersensitivity |
|
|
Term
| What are natural killer cells? |
|
Definition
-'innate immunity' cells which will kill cells which show signs of stress
-have inhibitory receptors to prevent activation & therefore prevent killing 'healthy' cells |
|
|
Term
| What do inhibitor receptors of killer cells recognize on healthy cells? |
|
Definition
| MHC self class I receptors on the healthy cells |
|
|
Term
| What roles do macrophages play in the early immune response? |
|
Definition
-induce secretion of IL-1 which activates T cells
-antigen presentation by internalizing the antigen and expressing the Ag on the surface to activate T cells & release lymphokines |
|
|
Term
| What are the two major types of dendritic cells? |
|
Definition
Interdigitating Dendritic Cells
Follicular Dendritic Cells |
|
|
Term
| What do Interdigitating Dendritic Cells do? (4 steps) |
|
Definition
-capture antigens in tissues
-migrate to lympgoid
-present the antigen to lymphoid T-cells
-trigger cytokine secretion |
|
|
Term
| What do follicular dendritic cells do? |
|
Definition
-capture complement proteins & Ab/Ag in lymphoid tissues
-present antigen to lymphoid B-cells |
|
|
Term
| What are the Antigen-Presenting cells? |
|
Definition
|
|
Term
| What are the 5 main classes of immunoglobulins & what are their key features? |
|
Definition
IgG
-colostrum immunity, opsonize microbes
IgA
-in mucosal tissues (respiratory & GI)
IgE
-coats parasites
IgM
-bacteria & viruses
IgD |
|
|
Term
| What gives immunoglobulins their specifity? |
|
Definition
| the AA sequence of the 'light' chain |
|
|
Term
| Where do complement proteins bind to an immunoglobulin molecule? |
|
Definition
| the 'constant' regions of the light & heavy chains |
|
|
Term
| How long does it take for antibodies to appear in the serum after exposure to an antigen? |
|
Definition
|
|
Term
| Why are Ig levels so low around 3-4 months of age? |
|
Definition
| maternally derived antibodies are decreasing yet the lymphoid tissue has not developed enough to produce its own antibodies |
|
|
Term
| What happens if non-specific defenses & non-specific immune response is not enough to stop antigens once they enter the body? |
|
Definition
| the antigens will enter the lymphatic system & travel to lymph nodes |
|
|
Term
| What happens to antigens when they reach the lymph nodes? |
|
Definition
-processed by macrophages & presented to T & B cells
-activated T cells are produced
-plasma cells are produced (secrete antibody)
-antibody enters efferent lymphatic vessels & enters blood plasma |
|
|
Term
| What is a 'hyperplasic' lymph node? |
|
Definition
| a lymph node with antigens which has stimulated lots of activity |
|
|
Term
| What is agglutination? Why is it important? |
|
Definition
formation of clumps of Ag & Ab complexes due to crosslinking between the complexes
-makes it easier for phagocytes to trap & consume immune complexes
-may neutralize toxic antigens |
|
|
Term
|
Definition
| coating the antigen with antibody to increase phagocytosis by leukocytes |
|
|
Term
| What is the 'Fc' portion of an immunoglobulin for? |
|
Definition
| the portion that will be recognized by leukocytes with receptors specific to that antibody |
|
|
Term
| What is complement fixation? |
|
Definition
| -9 plasma proteins which react in sequence to form a cytotoxic complex which can lyse a cell membrane |
|
|
Term
| What are the effects of complement activation? |
|
Definition
-complement fixation
-C3a/C5a = vasodilation & permeability, chemotactic
-C3b is an opsonin |
|
|
Term
True or False
agglutination & opsonization occur only if the antigen is a macromolecule |
|
Definition
false
only if the antigen is cellular |
|
|
Term
| What happens if the antigen is a macromolecule? |
|
Definition
| Ag-Ab complexes form, create a large macromolecular complex to make phagocytosis easier |
|
|
Term
| What are the characteristics of an immune response? |
|
Definition
specificity
memory
amplification (enhanced response on second exposure to antigen) |
|
|
Term
| What is happening during the 'lag' period of a primary immune response? What Ig is produced first? |
|
Definition
B cells are undergoing clonal expansion to produce lots of plasma cells which secrete the specific antibody
IgM first |
|
|
Term
| What immunoglobulin is produced mainly during the secondary immune response? |
|
Definition
|
|
Term
| What are some examples of passive immunity? |
|
Definition
Transplacental (IgG across placenta in-utero)
Colostral (Ig through milk)
Therapeutic (administration eg. snake antivenins) |
|
|
Term
True or False
Passive immunity has very long effects |
|
Definition
false
it will be metabolized by the body, is short-acting |
|
|
Term
| What is an attenuated vaccine? |
|
Definition
| vaccine with an organism that has been rendered harmless |
|
|
Term
| The toxin/organism in a vaccine retains its _____ but not its ______ |
|
Definition
| antigenicity but not its pathogenicity |
|
|
Term
| Why are vaccines administered in a series to young mammals? |
|
Definition
-need to vaccinate when maternal antibodies e declining otherwise they will block the vaccine
-lots of variability in the time for this between individuals, so we give a series to allow for room for errow |
|
|
Term
| studying antigen-antibody reactions in a lab setting is known as.... |
|
Definition
|
|
Term
|
Definition
| the dilution at which the reactivity between Ag & Ab is not affected |
|
|
Term
True or False
A low titer indicates high antibody levels |
|
Definition
false
high antibody levels |
|
|
Term
| What is hypersensitivity? |
|
Definition
| when an immune response is so reactive that it leads to tissue injury |
|
|
Term
| What are the 4 types of hypersensitivity reactions and how are they mediated? |
|
Definition
Anaphylactic
Antibody-Dependent
Complex-mediated
Cell-mediated
Types I, II & III: mediated by antiobody reactions
Type IV: cell mediated responses |
|
|
Term
| What are the two types of Type I Sensitivity? |
|
Definition
|
|
Term
| What would happen during the first exposure to an antigen in an individual with Type I Localized Hypersensitivity? |
|
Definition
1. Allergen introduced
2. Th2 cells activated
3. IgE produced
4. Cytokine secretion
5. IgE binds to Fc receptors on mast cells |
|
|
Term
| What would happen during the second exposure to an antigen in an individual with Type I Localized Hypersensitivity? |
|
Definition
1. Allergen activates mast cells tagged with the IgE
2. Mediators secreted which cause pathological manifestations of immediate hypersensitivity |
|
|
Term
| What happens during the late-phase reaction of Type I hypersensitivity? |
|
Definition
-eosinophils, neutrophils & lymphocytes infiltrate tissue
-epithelial damage
-bronchospasm |
|
|
Term
| What is the initial response of Type I hypersensitivity? (3) |
|
Definition
vasodilation
vascular leakage
smooth muscle spasm |
|
|
Term
True or False
Anaphylaxis is associated with Type I Localized Hypersensitivity |
|
Definition
|
|
Term
| What happens during secondary exposure to an allergen in Type I hypersensitivity, in regards to mast cells? |
|
Definition
| the IgE coating mast cells cross links with Fc triggering release of mediators |
|
|
Term
| What are the primary mediators released from mast cells? |
|
Definition
| -histamine, proteases, chemotactic factors |
|
|
Term
| What are secondary mediators? |
|
Definition
Generated mediators produced by activation of Phospholipase A which targets arachidonic acid metbolism
-secrete cytokines, chemokines, prostaglandins etc. |
|
|
Term
| What are the 3 mechanisms that might cause Type II Hypersensitivity? |
|
Definition
Opsonization & Phagocytosis
Inflammation
Antibody-Mediated Cellular Dysfunction |
|
|
Term
| Why might opsonization cause Type II hypersensitivity? |
|
Definition
-cells coated with Ab are opsonized (more susceptible to phagocytosis
-body might mistake a normal cell surface component as being foreign & phagocytize it |
|
|
Term
| Why might inflammation cause Type II hypersensitivity? |
|
Definition
-antibodies bound to antigens activate the complement system
-complement products recruit neutrophils & monocytes triggering inflammation
-products also opsonize cells & can lyse cells (especially RBCs) |
|
|
Term
| What Antibody-Mediated Cellular Dysfunction? |
|
Definition
-antibodies can be formed against cell surface molecules/receptors to inhibit cell function without causing necrosis
e.g. Myaesthenia gravis = antibodies against Ach receptors = muscle weakness |
|
|
Term
| What is Type III hypersensitivity? |
|
Definition
-an antigen elicits formation of an antibody
-the interaction between the Ag & Ab form complexes which are deposited in walls of small vessels
-this activates complement, acute inflam & tissue injury |
|
|
Term
| Why does Type II hypersensitivity cause tissue injury? |
|
Definition
| neutrophils are recruited to phagocytize the immune complexes which causes secretion of pro-inflammatory substances |
|
|
Term
| What is the end result of immune-complex mediated hypersensitivity? |
|
Definition
-fibrinoid necrosis of small vessels
(necrotizing vasculitis) |
|
|
Term
| What happens if an immune-complex mediated hypersensitivity occurs in the renal glomerular vessels? |
|
Definition
|
|
Term
| What is fibrinoid necrosis? |
|
Definition
| necrosis of collagen & smooth muscle, has a homogenous fibrin-like appearance |
|
|
Term
| What type of hypersensitivity is associated with hypersensitivity pneumonitis? |
|
Definition
|
|
Term
| What are the two types of Type III hypersensitvity? |
|
Definition
| Localized & Systemic Immune Complex Disease |
|
|
Term
| What is Local Immune Complex Disease? |
|
Definition
necrosis occurs at site of antigen antry
repeated exposure = lots of specific antibody in the serum
-future exposure will lead to Ag/Ab complexes deposited in small blood vessels leading to local tissue necrosis |
|
|
Term
| What is Systemic Immune Complex Disease? |
|
Definition
-exposure to large dose of an antigen produces an antibody
-Ag/Ab complexes are formed in the blood
-if more Ag than Ab the complexes formed are soluble and can pass through pores & be deposited in vessel walls
-leads to vascular necrosis |
|
|
Term
| Why is an excess of Ab during the formation of Ag/Ab complexes not a significant concern? |
|
Definition
| cannot pass through endothelial pores as complexes are large, are removed by mononuclear phagocytes |
|
|
Term
| Where are immune complexes typically deposited? |
|
Definition
in walls of vascular system, especially small vessels
also kidneys & joints |
|
|
Term
| What is Type IV Hypersensitivity? |
|
Definition
| -sensitized T cells are either directly cytotoxic or secrete cytokines which recruit effector cells that cause injury |
|
|
Term
| What cells characterize Delayed Type Hypersensitivity? |
|
Definition
|
|
Term
| What happens when a sensitive person undergoes exposure poison ivy? |
|
Definition
1. Naive CD4 cells recognize antigens, create memory CD4 cells, Th1 effectors
2. Subsequent exposure triggers cytokine excretion
3. IFN-Y activates macrophages which produce tissue-damaging substances & promote fibrosis & inflammation |
|
|
Term
| What cytokines are primarily responsible for the development of the DTH response? |
|
Definition
IL-12: drives T cells along Th1 pathway
IFN-Y: activates macrophages/enhances phagocytosis
IL-2: proliferation of T cells
TNF & lymphotoxin: vasodilation, leukocyte attachment |
|
|
Term
| What type of hypersensitivity is useful in diagnosing whether people have been exposed to tuberculosis? |
|
Definition
|
|
Term
True or False
DTH is important in granulomatous inflammation |
|
Definition
|
|
Term
| What cells characterize T cell-mediated cytotoxicity? |
|
Definition
| CD8+ cells (cytotoxic T cells) |
|
|
Term
| What causes necrosis of cancer cells? |
|
Definition
| T-cell mediated cytotoxicitiy |
|
|
Term
|
Definition
| tissue graft between two individuals of same species but with different genotypes |
|
|
Term
| What is the role of histocompatibility molecules? |
|
Definition
| bind peptide fragments of foreign proteins for presentation to antigen-specific T cells |
|
|
Term
|
Definition
aka histocompatibility antigens
-antigens on surfaces of nucleated cells |
|
|
Term
|
Definition
-encodes 3 classes of molecules
Class I (HLA) found on all tissues
Class II on antigen-presenting cells & B cells |
|
|
Term
| What determines the success of a tissue graft? |
|
Definition
| similarity between donor & recipient of the antigens encoded by the major histocompatibility complex |
|
|
Term
| How does Type IV hypersensitivity lead to classic acute rejection? |
|
Definition
-T cells destroy the parenchyma & endothelial cells of the grafted tissue
-T cells damage graft vasculature |
|
|
Term
| Hyperacute rejection occurs when... |
|
Definition
| preformed antibodies bind to the graft endothelium causing ischemia & thrombosis |
|
|
Term
| What are the two types of tissue rejection? |
|
Definition
T Cell-Mediated Rejection
Antibody-Mediated Rejection |
|
|
Term
|
Definition
inactivation of lymphocytes
-induced by exposure to antigens under certain conditions |
|
|
Term
| What are primary immunodeficiency diseases? |
|
Definition
| genetically determined diseases which affect humoral or cellular immunity, or non specific host mechanisms e.g. complement/phagocytes/NK cells |
|
|
Term
| What type of immunity defect is affected by SCID? |
|
Definition
| defects in both humoral and cell-mediated immunity |
|
|
Term
| What are secondary immunodeficiencies? |
|
Definition
| immune deficiencies due to malnutrition, cancers, infection, radiation etc. |
|
|
Term
|
Definition
| infection with the retrovirus HIV |
|
|
Term
| How does HIV lead to AIDS? |
|
Definition
| HIV incorporates itself into the cellular DNA, influencing cell function & integrity |
|
|
Term
True or False
AIDS can lead to cancers & neurologic signs |
|
Definition
|
|
Term
| What are the 3 major routes of HIV transmission? |
|
Definition
Sexual
Parenteral (blood, needles)
Mother-to-Infant |
|
|
Term
| What is the importance of glycoproteins in HIV? |
|
Definition
| critical for infection of cells |
|
|
Term
|
Definition
| a core protein of HIV that is a readily detected antigen |
|
|
Term
| Why is the HIV virus difficult to develop a vaccine for? |
|
Definition
-genome encodes for various proteins, as well as regulates assembly of viral particles
-lots of variability in the genome |
|
|
Term
| Which cells does AIDS show a tropism for? |
|
Definition
|
|
Term
| What is the defining characteristic of AIDS? |
|
Definition
| loss of CD4+ cells leading to increased susceptibility to pathogens & cancers |
|
|
Term
| What causes a loss of CD4+ cells in AIDS? |
|
Definition
increased destruction of infected cells
reduces production of CD4 cells |
|
|
Term
| What cells are affected by HIV? How? |
|
Definition
monocytes (reservoirs)
macrophages (reservoirs, transportation)
CD4+
Dendritic cells (transport to lymph nodes) |
|
|
Term
| What are the 3 phases of HIV infection? |
|
Definition
Early Acute: self-limiting, can detect virus-specific antibodies
Middle Chronic: HIV test is positive but few signs of disease, virus replicates in lymph tissues
Crisis phase: severe opportunistic infections, very low CD4+ count, severe viremia |
|
|
Term
|
Definition
AIDS-related complex
patients are HIV+, symptomatic but dont have any indicator diseases of AIDS such as opportunistic infections, lymphoma |
|
|
