Microbiology Ch17 Adaptive Immunity pt2

Classes of T cells (2)

(CD = cluster of differentiation)

- CD4

- CD8

CD4 T cells (3)

- t-helper cells (T^h)

- bind MHC class II molecules on B cells & APCs

- cytokine signaling with B cells; interact DIRECTLY with antigens

CD8 t cells (2)

- cytotoxic t cells

- bind MHC class I molecules

TCR on T^h cell function (2)

- recognize & bind to the antigen fragment & MHC class II on APC

- APC or Th secretes a costimulatory molecule -> activates the T^h cell

T^h cell function

prod. cytokines

T^h cells differentiate into (4)

- Th1 cells

- Th2 cells

Th17 cells

- memory cells

T regulatory cells (2)

- subset of CD4; additional CD25 molecule

- helps regulate immune responses

T regulatory cells function (3)

- suppress itself

- ignores normal flora (prot. intestinal bacteria)

- protects fetus

Cytotoxic T lymphocytes (CTL)

activation of naive Tc cell

How are cytotoxic t lymphocytes (CTL) activated

TCR interacts w/ class I MHC & antigenic peptide (endogenous antigen) presented on another body cell

CTL function (2)

- recognize other cells expressing same antigen -> target cells may harbor an intracellular pathogen (virus, tumor)

- attack target cell w/ preforin (forming a pore) and granzymes (proteases) causing apoptosis

Apoptosis of CTL (3)

- programmed cell death

- prevents spread of infectious viruses into other cells

- cells cut their genome into fragments, causing membranes to bulge outward via blebbing

NK (Natural killer) cells (3)

- dont need stim. by antigen

- detects if cells express MHC class I or not (viral-infected/tumor cells dont express MHC class I)

- destroy virus-infected cells, tumor cells, & large, extracellular parasites

antibody-dependent cell-mediated cytotoxicity (3)

- protozoans and helminths are too large to be phagocytized (coated with antibodies)

- immune system cells (NK cells, macrophages) attach to the Fc regions of antibodies

- target cell is lysed by chemicals secreted by the immune system cels

Immunological memory primary response

immune response on first exposure to an antigen

Immunological memory secondary (memory/anamnestic) response

occurs after the 2nd exposure to an antigen

Immunological memory secondary vs primary response

secondary:

- class switching

- more rapid, longer, greater in magnitude

- memory cells produced

Immunological memory class switching

initial IgM response shifts to IgG, IgE, IgA (change

Antibody titer

relative amount of antibody in the serum (reflects intensity of humoral response)

Types of adaptive immunity

- naturally acquired active immunity

- naturally acquired passive immunity

- artificially acquired active immunity

- artificially acquired passive immunity

naturally acquired active immunity

result from infection

naturally acquired passive immunity

transplacental (birth) or colostrum (breast milk)

artificially acquired active immunity

vaccination (immunization)

artificially acquired passive immunity

injection of antibodies (rabies -> inject antibodies to catch rabies virus before it takesover)