Chapter 4 - Immunology Flashcards
What is IL-4? what does it do?
Released by CD4 helper T cell
Causes B-cell maturation into plasma cells
What is IL-2? what does it do?
Released by CD4 helper T.
Causes maturation of cytotoxic T cells.
Involved in delayed hypersensitivity. (brings in inflammatory cells by chemokine secretion)
What do Th1 helper T-cells do? examples?
Predominant release of proinflammatory cytokines (IL-2, INF-gamma). Cell mediated responses against intracellular bacteria and protozoa.
Work with cytotoxic CD8 and macrophages.
Overactivation - Type 4 delayed-type hypersensitivity - Type 1 DM
(IL-2 involved in B cell maturation to plasma cells)
(Cell mediated responses involved in TB, viruses, intradermal skin test)
What do Th2 helper T-cells do? examples?
Predominant release of anti-inflammatory cytokines (IL-4 inhibits macrophages).
Humoral response against extracellular parasites - helminths.
Overactivation - Type 1 hypersensitivity - atopy and allergic responses (IL-4 - B-cell - IgE - mast cell release of histamine, serotonin)
(IL-4 also involved in B cell maturation into plasma cell)
What do Suppressor T cells (CD8) cells do?
Regulate CD4 and CD8 cells
What do cytotoxic T cells (CD8) do?
(Maturation by IL-2)
Recognize and attack non-self antigens attached to MHC- class 1 receptors (eg viral gene products)
What does an intradermal skin test look for?
cell-mediated immunity
What types of infections are associated with defects in cell-mediated immunity?
intracellular pathogens (TB, viruses)
(why TB tested by intradermal skin test)
What effect can nucleotides have on the immune response?
increase T-cell mediated immunity
(intradermal skin test, TB, viruses)
What is the first step in T-cell and B-cell activation?
alloantigen binds to antigen specific receptors: TCR (t-cells) or surface IgM (B-cells).
What is the second step or costimulatory signal required for T-cell and B-cell activation?
IL-1 released by antigen presenting cell.
CD-41 helper T-cells release IL-2, IL-4, and IL-5 which provide help for CD81 T-cells and for B-cell activation.
(IL-1 - fever, IL-2 - cytotoxic T cell maturation, IL-4 - B cell to plasma cell)
What does MHC class I (A, B, and C) do? Where is it present? Structural makeup? What is it a target for?
CD8 cell activation. On all nucleated cells. Single chain with 5 domains. Its a target for cytotoxic T-cells.
(Cytotoxic T cells matured by IL-2, CD8 can be cytotoxic or suppressor. Cytotoxic cells recognize non-self antigens, like virus, on MHC1 presenting cells)
What does MHC class II (DR, DP, and DQ) do? where is it located? structural makeup?
CD4 cell activation. Present on B-cells, dendrites, monocytes, and antigen presenting cells. 2 chains with 4 domains each. Activator for helper T-cells. Stimulates antibody formation.
How are viral infections recognized by immune system?
Endogenous viral proteins are produced, bound to class I MHC, go to cell surface, recognized by CD8 cytotoxic T-cells.
How are bacterial infections recognized by immune system?
endocytosis, proteins bound to class II MHC molecules, go to cell surface, recognized by CD4 helper T-cells -> B cells already bound to antigen are then activated by CD4 helper T-cells. They then produce the antibody to that antigen and are transformed to plamsa cells and memory B-cells
Do natural killer cells require MHC?
Do not require MHC, previous exposure, or antigen presentation. Not considered T or B. Recognize lack of self MHC. Cancer surveillance.
What is IgM?
Initial ab made after exposure to antigen. Largest Ab. 5 domains, 10 binding sites.
What is IgG?
Most abundant antibody in the body. responsible for secondary immune response. Can cross placenta - protection in newborn period.
What is IgA?
Found in secretions. Peyers patches in gut - prevents microbial adherence and invasion in gut; and in breast milk - additional immunity in newborn.
What is IgD?
membrane-bound receptor on B-cells (antigen receptor)
what is IgE?
allergic reactions, parasite reactions
What antibodies are opsonins?
IgM and IgG. Fix complement. 2 IgG’s or 1 IgM
What does the variable region in an antibody do?
antigen recognition
What does the constant region in Ab do?
Recognized by PMN and macrophages. Fc fragment does not carry variable region.
What are polyclonal antibodies?
have multiple binding sites to the antigen at multiple epitopes
What are monoclonal antibodies?
have only 1 binding site to 1 epitope
How are variable and constant regions of heavy and light chains bound?
disulfide bonds
What is a type 1 hypersensitivity reaction?
Immediate. allergic. TH2 and IgE mediated - mast and basophils relase histamine, serotonin and bradykinin in response to releas of major basic protein from eosinophils which have IgE receptors for antigen. (Bee stings, hay fever, peanuts, atopy)
What is a type 2 hypersensitivity reaction?
IgG or IgM reacts with cell-bound antigen
(ABO, Rh, Graves, Myasthenia gravis, ITP)
What is a type 3 hypersensitivity reaction?
Immune complex deposition
(serum sickness, rheumatoid, SLE)
What is a type 4 hypersensitivity reaction?
Delayed-type hypersensitivity. Ag stimulation of sensitized T-cells
(TB skin test, contact dermatitis)
What are basophils the major source of?
Histamine in the blood
(Assn: TH1, IgE, allergy, Type-1 hypersensitivity)
What are mast cells the major source of?
Histamine in tissue (other than stomach)
What are primary lymphoid organs?
liver, bone, thymus
What are secondary lymphoid organs?
spleen and lymph nodes
What is immunologic chimera?
2 different cell lines in one individual (bone marrow transplant recipient)
What do you do for non-tetanus prone wounds?
Give tetanus toxoid only if patient has received <3 doses or tetanus status unknown
What do you do for tetanus prone wounds?
>6 hr old, gross contamination, crush, burn, frostbite, missile wound
alway give tetanus toxoid unless known to have >3 ant it has been <5 years since last booster
Tetanus immune globulin is given when?
patient with tetanus prone wounds who have not been immunized
