I. Innate vs. Acquired Immunity
- Innate- born with; defenses against pathogens in general— conserved across species beyond vertebrates
- Acquired- "adaptive"; exposure to particular pathogens leads to immunity against that pathogen- specified for each particular pathogen; only found in vertebrates (acquired immunity requires a timeframe to develop and is only effective if reexposure occurs to the same pathogen, this means the host must generally have a larger lifespan)
II. Innate immunity overview
i. Inflammation: rubor calor, tumor, dolor (rubor= redness; calor=heat; tumor=enlarged; dolor=pain)
* Symptoms due to:
-increase in blood flow to damaged site
-increase in vascular permeability
-pain from chemicals (to prevent further damage)
1. cytokines: "cell mover"- chemicals that recruite immune cells to site of damage
*change behavior of cell
*cytokines lead to differentiation of immune ell types (diagram p. 5)
[Lymphoid=acquired immune cells; erythroid; myeloid=innate immune cells]
ii. Innate immune tissues and cells
1. Barriers
a. Skin/other epithelia
*skin: dead cells = great protection
*live epithelia: have very tight junctions btw. Cells
b. Mucous membrane
*sticky, dense, watery
*traps microbes
*cough up and out or swallow to kill microbes in it w/low pH of gut
c. Cilia epithelial
*sweep microbs up and out
*also can stop microbe sticking to cell surface
2. Antimicrobial chemicals
a. Lysozyme
*found in blood, sweat, & tears
*brings down links between peptigloglyican (cross-links)
*breaks cell wall, osmotic pressure makes bacteria go bye bye)
**don’t work on gram (-) bacteria because of their outer membrane
b. Complement and membrane attack complex (MAC)
*C3b of complement can bind to outside of microbes
*acts as a handle for phagocytes to hold on to => opsonin
*component of can form MAC
*MAC: large hole in cell membrane
*open holes in gram (-) outer membrane so lysozyme can work
3. Myeloid cells: derived from hematopoitic stem cell, innate immune system, originally arise in bone marrow
a. Macrophages
*large phagocytes
*circulating (in blood)
*resident in tissues
*derived from monocyte
*refer to Fig. 1.4 in text
*Physical characteristic: round nucleus
b. Granulocytes
*dark-staining granules that contain inflammatory mediators, especially cytokines
i. Neutrophils (polymorphonuclear cells of PMNs)
*neutral stained
*kind of phagocyte
*engulf bacteria & kill with antibacterial components of granules
*made on demand (i.e. in response to bacterial components)
*fairly short lived: live ~2 days; circulate in blood with lobed nuclei
ii. Basophils
*basic stain
*in blood
*made on demand
*made granules than neutrophils
1. Mast cells
*many granules
*resistant in tissue
*main component in granules: histamines
iii. Eosinophils
*in blood
*made on demand
Basophils including mast cells, and Eosinophils: kill things too large to be engulfed by releasing antimicrobial chemicals in granules into environments. Ex. parasites
*http://content.answers.com/main/content/wp/en-commons/2/20/Illu_blood_cell_lineage.jpg (link to image of different cells being discussed)
**Note: The diagram linked above, while somewhat helpful, is oversimplified and incorrect in some respects. For instance, megakaryocytes are of the erythroid lineage, not their own separate lineage, as this diagram implies.
III. Acquired Immune Tissues and Cells
1. Lymphatic system
- returns liquid that seeps out of blood vessels back into circulation
- allows immune cells into tissues
2. Lymphoid Cells
- "naive" - haven't been exposed to pathogen
- "mature" - have been exposed to pathogen and is differentiated
A. B-cells - differentiate in bone marrow, when mature they differentiate into:
- plasma cells - secrete antibodies
- antibody - sticks to a particular chemical motif (antigen) of a particular pathogen
- antigen vs. epitope
- antigen - what antibody sticks to
- epitope - part of antigen that antibody sticks to
B. T-cells - differentiate in thymus
- activate B-cells to produce antibodies
- activate phagocytes to ingest and destroy microorganisms
C. "Natural Killer" cells - lymphocytes lacking antigen specific receptors but with invariant receptors that detect infected cells and some tumor cells and activate their destruction
