Unit 3 Immune Flashcards
immunity
ability of an organism to respond to and repel invasion by forming substances
innate (nonspecific) immunity
physical barriers
secretions with antimicrobial activity
acquired (adaptive, specific) immunity
specific, directed toward specific agent
cells required for acquired immunity
- presenters of foreign substance to responders
- responders that produce antibodies
- responders that destroy infected cells
innate surface barriers
skin
mucous membranes
innate internal defenses
phagocytes fever NK cells antimicrobial proteins inflammation
humoral immunity
adaptive
B cells
cellular immunity
adaptive
T cells
antigens
a. substances that can mobilize immune response
b. may be soluble or attached to cell
c. may be proteins, polysaccharides, or lipids
d. contain epitopes
e. can be self-antigen
types of antigens
complete
hapten (incomplete, must be bound to body’s self protein)
epitope
antigenic determinants
specific portion of antigen recognized
antibody characteristics
a. produced by plasma cells
b. glycoproteins of immunoglobulin family
c. soluble or attached to surface of lymphocytes
d. recognized bind to specific epitope
antibody structure
- multimeric protein (2 light/heavy proteins)
- Fc region
- Fab region
Fab region
a. antigen binding
b. hypervariable
c. two per molecule
IgM
- first antibody produced in initial immune response
- bound to B lymphocytes
- stimulates clonal expansion and differentiation of plasma cells
IgG
- most abundant antibody in blood
- produce in late primary and secondary response
- facilitates destruction of bacteria and viruses
IgE
- Fc region binds to receptors on mast cells and basophils
- low levels in blood
- antibody-mast cell complex stimulates release of histamine and other molecules
IgA
- in secretions (saliva, tears, etc.)
- enzyme resistant
- active against bacteria and viruses
IgD
very low concentration, mostly bound to B lymphocytes
lymphocyte characteristics
- multiple subpopulations
2. distinguished by membrane proteins; cluster differentiation markers, receptors
T lymphocytes
a. T cell receptor (TCR) on cell surface
b. only recognize epitopes bound to receptors (MHC) molecules on other cells
c. subpopulations distinguished by CD markers
CD 4
helper T cells; central to immune response; coordinate response of other lymphocytes
CD 8
cytotoxic T cells
T supressor cells
cytotoxic T cells
involved in cell-mediated response
T supressor cells
turn off response
B lymphocytes
- IgM bound to surface with Fab fragment exposed
- recognized epitope becomes activated
- clonal expansion
- differentiate into plasma cells and memory B cells
- anamnestic response
clonal expansion
proliferation of activated B cells
anamnestic response
powerful response to second exposure
MHC characteristics
a. integral membrane proteins
b. combine with peptides derived from viruses or other foreign substances
c. display forming antigens on cell surface
MHCI
a. found on cell surfaces
b. present antigent to cytotoxic T cells
MHCII
- found on antigen presenting cells – macrophages, dendritic cells, activated T cell, etc.
- presentation to helper T cell is central to coordinating immune response
antigen presenting cells (APC)
macrophage
T helper cell (CD4)
macrophage
- ingestion and partial digestion of foreign substance
2. presentation of foreign material on surface by MCHII
T helper cell (CD4)
- recognizes MHCII-antigen complex
- binds to macrophage
- activates cytotoxic T cells
- activates B cells to create plasma cells generating antibodies
primary response
- takes about two weeks to develop peak antibody levels and activities (titers).
- IgM and IgG antibody concentrations do not remain elevated.
secondary response
- characterized by a very rapid increase in IgG antibody concentration and titer, rises to levels much higher than those of the primary response.
- Antibody activity remains elevated for an extended period after the second exposure to the antigen.
roles of helper T cells
- Activate both humoral and cellular arms
- Once primed by APC presentation of antigen, helper T cells:
a. Help activate B cells and other T cells
b. Induce T and B cell proliferation
c. Secrete cytokines that recruit other immune cells
3 Without TH, there is no immune response
phagocytic cells
neutrophils
macrophages
Langerhan’s cells
dendritic cells
removal of bacteria
by neutrophils:
margination
diapedesis
margination
attraction of circulating neutrophils:
a. endothelial cells secrete attractant molecules
b. neutrophils slow and briefly adhere to endothelium
diapedesis
movement of neutrophils between endothelial cells into connective tissue
