Chapter 4: Immunology Flashcards
- Release IL-2 (causes maturation of cytotoxic T cells)
- Release IL-4 (causes B-cell maturation into plasma cells)
- Involved in delayed-type hypersensitivity
Helper T cells (CD4)
Causes maturation of cytotoxic T cells
IL-2
Causes B-cell maturation into plasma cells
IL-4
Brings in inflammatory cells by chemokine secretion
Delayed-type hypersensitivity
Regulate CD4 and CD8 cells
Suppressor T cells (CD8)
Recognize and attack non-self-antigens attached to MHC class 1 receptors (e.g. viral gene productS)
Cytotoxic T cells (CD8)
Used to test cell-mediated immunity
Intradermal skin test (i.e., TB skin test)
Infections associated with defects in cell-mediated immunity
Intracellular pathogens (TB, viruses)
- CD8 cell activation
- Present on all nucleated cells
- Single chain with 5 domains
- Target for cytotoxic T cells (binds T cell receptor)
MHC class 1 (A, B, C)
- CD4 cell activation
- Present on antigen-presenting cells (e.g., monocytes, dendrites)
- 2 chains with 4 domains each
- Activates helper T cells (binds T cell receptor)
- Stimulates antibody formation after interaction with B cell surface IgM
MHC class II (DR, DP, and DQ)
Mechanism of immune response to viral infection
Endogenous viral proteins are produced, are bound to class I MHC, go to cell surface, and are recognized by CD8 cytotoxic T cells
Mechanism of immune response to bacterial infection
Endocytosis, proteins get bound to Class II MHC molecules, go to cell surface, recognized by CD4 helper T cells -> B cells which have already bound to the antigen are then activated by the CD4 helper T cells; they then produce the antibody to that antigen and are transformed to plasma cells and memory B cells.
- Not restricted by MHC, do not require previous exposure, do not require antigen presentation
- Not considered T or B cells
- Recognize cells that lack self-MHC
- Part of the body’s natural immunosurveillance for cancer
Natural Killer Cells
Initial antibody made after exposure to antigen. It is the largest antibody, having 5 domains (10 binding sites)
IgM
Most abundant antibody in body.
Responsible for secondary immune response.
Can cross the placenta and provide protection in newborn period.
IgG.
What type of cells do natural killer cells recognize?
Recognize cells that lack self-MHC
Two signals that cause activation of T and B cells
- Alloantigen binds to antigen specific receptors. (TCR - T cells; IgM - B cells)
- IL-1 release by APC.
CD4 helper T cells release IL-2/4 which provide help for CD8 T cells and B-cell activation.
Endogenous antigen processing and presentation
Endogenous proteins are degraded into peptides that are transported to ER. Peptides bind to MHC-1 and transported to surface of APC. CD8 cells recognize complex by way of TCR complex.
Exogenous antigen processing and presentation
Exogenous antigen is broken down into peptide fragments in endosomes. Class-2 molecules transport to endosome, bind the peptide, and delivered to surface of APC cell, where they are recognized by CD4+ cells.
Found in secretions, in Peyer’s patches in gut, and in breast milk (additional source of immunity in newborn); helps prevent microbial adherence and invasion in gut.
IgA
Membrane-bound receptor on B cells (serves as an antigen receptor)
IgD
Allergic reactions, parasite infections
IgE
Opsonins
IgM, IgG
Fix complement
IgM, IgG (requires 2 IgGs, or 1 IgM)