ianroo

INNATE                                 ADAPTIVE
----------------------------------------------------------
pattern recognition                 antigen-specific
immediate                             delayed
no memory                            immunological memory

INNATE:
- 1st line of defense
- not specific to particular pathogen
- components present before onset of infection
- recognize patterns unique to microbes such as
     - soluble molecules
     - cell-associated receptors (Toll-like receptors = TLRs)
- occurs before adaptive immune system
- some natural barriers
     - skin, mucosal membranes
     - acidity of stomach & perspiration
     - lysozyme in tears

ADAPTIVE:
- after there is a recognized antigenic challenge (antigen-specific)
- 4 characteristic attributes
     - antigenic specificity
     - diversity
     - immunological memory
     - self-non-self recognition
- 2 arms
     - humoral immune responses
          - effector molecules = antibodies produced by B lymphocytes
     - cell-mediated responses
          - effector molecules = both T helper (TH) & cytotoxic T lymphocytes (CTLs)

STEM CELLS: DEVELOPMENT OF IMMUNE SYSTEMS
- in adult bone marrow
- 2 main characteristics
     - differentiate into all other cell types
     - self-renewing, maintain population level by cell devision
- human development
     - 1st few weeks: in embryonic yolk sac
     - 3 month: migrate to fetal liver 
     - 3 ~ 7 month: into spleen, hematopoesis during this period