The document summarizes the basic concepts of immunity. It describes innate immunity as the first line of defense mechanisms that are always present, including epithelial cells, phagocytes, natural killer cells, and complement proteins. Adaptive immunity develops later after exposure to microbes and involves lymphocytes and antibodies that provide highly specific and powerful immune responses. The adaptive immune system consists of T lymphocytes and B lymphocytes that recognize antigens through receptor proteins.

4.  Two edged sword: Vital to survival, Harmful when excess.
 immunity- Immunodeficiency- render Humans easy prey to
infections and possibly tumors;
 immunity- Hypersensitivity; fatal allergic reaction to sting bite.
 Autoimmune rn: Reaction against one’s own tissues and cells.
BASIC CONCEPTS OF IMMUNITY

5. 1. INNATE IMMUNITY (NATURAL/ NATIVE):
 Defense mechanisms that are present even before infection.
 First line of defense; Not specific to any microbe
2. ADAPTIVE IMMUNITY (ACQUIRED/ SPECIFIC):
 Mechanisms that are stimulated by microbes and are capable
of also recognizing non-microbial substances (antigens).
 Develops later after infection
 More specific and more powerful.

6. First line defense: it is always ready to prevent and eradicate
infections.
Components:
1. Epithelial cells
2. Phagocytic cells
3. NK –natural killer cells
4. Plasma proteins and complement system
Body defense
mechanisms

7.  Develops later after exposure to microbes
 Even more powerful in combating infections.
 Consists of Lymphocytes and their products
(antibodies).

9.  Generated from immature precursors in the thymus
 Found in :
1. BLOOD- 60-70% of lymphocytes
2. LN- Paracortical areas
3. SPLEEN- Periarteriolar lymphoid sheath (PALS).
 Contains T Cell Receptor (TCR)

10. T LYMPHOCYTES
CD 4
60%
CD 8
40%
MHC
CLASS II
HELPER CYTOTOXIC
TH 1 CELLS: IL-2, IFN
TH 2 CELLS: IL-4,5,13
IL-2, IFN gamma.
MHC
CLASS I

11. MHC
ANTIGEN
PRESENTATION
COMPONENTS OF
COMPLIMENTS
CLASS IIICLASS IICLASS I
(ALL NUCLEATED
CELLS)
(MACROPHAGES,
DC, EC’S)
HLA
A,B,C
HLA-D
ALPHA & BETA
DP
DQ
DR
CD-8 T
CELLS CD-4 T CELLS

12.  Master regulator / Conductor of Symphony Orchestra
 T cells secrete cytokines
 CD 4 TH-1 cell secretes IL-2 & IFN .
 CD 4 TH-2 cell secretes IL-4, 5, 13.
 The cytokines influence T cells, B cells, Macrophages & NK cells
 CD4 T cell is crippled in HIV infection

13.  Short acting soluble mediators.
 Paracrine, Autocrine, Endocrine effects.
 Recombinant cytokines Immunotherapy in cancers

14.  Develop from Immature precursors in BM
 10 -20% of peripheral blood lymphocytes
 Superficial cortex, follicles of lymph node & White pulp of
spleen
 After antigenic stimulation, B cells form Plasma cells that
secrete Immunoglobulins
B - LYMPHOCYTE

15. ANTIGENS
(PROTEINS AND NON-PROTEIN SUBSTANCES)
B-LYMPHOCYTE
ACTIVATION
DIFFERENTIATION
PLASMA
CELLS IMMUNOGLOBULINSImmunoglobulins
G.A.M.D.E.

16.  5% -15% of peripheral blood lymphocytes
 Larger than small lymphocytes, azurophilic granules
Large Granular Lymphocytes
 Innate immunity: Kill tumor cells, Virally infected cells.
 NK cells are CD 16, CD 56 positive .

18.  Part of Mononuclear Phagocyte system
 Induction of Cell mediated immunity
 They ingest protein antigens, process & present the peptide
fragments to T cells
 Important role in Type IV hypersensitivity, activated by IFN 
secreted by CD 4 TH-1
 Can phagocytose opsonized or Ig coated microbes

19.  Blood: Monocytes
 Brain: Microglial cells
 Lung: Alveolar macrophages/ Dust cells/ Heart failure cells
 Liver: Kupffer cells
 Spleen: Splenic sinusoidal macrophages
 Kidney: Mesangial Cells
 Lymph node: Sinus Histiocytes
 Skin: Interdigitating Dendritic Cells
 Bone: Osteoclastic giant cells
 Joint: Synoviocytes
 APC’s.

20. LPS
TOLL LIKE
RECEPTORS ON
MACROPHAGES
NUCLEAR FACTOR
ACTIVATION
CYTOKINE PRODUCTIONS
HYDROLYTIC ENZYMES, REACTIVE OXYGEN SPECIES
P H A G O C Y T O S I S

21. Innate Immunity --vs.-- Acquired Immunity