IMMUNITY• INNATE (present before birth,

“NATURAL”)

•ADAPTIVE (developed by exposure to pathogens, or in a broader sense, antigens)

INNATE IMMUNITY• BARRIERS• CELLS: LYMPHOCYTES, MACROPHAGES,

PLASMA CELLS, NK CELLS• CYTOKINES/CHEMOKINES• PLASMA PROTEINS: Complement,

Coagulation Factors• Toll-Like Receptors, TLR’s

ADAPTIVE IMMUNITY

•CELLULAR, i.e., direct cellular reactions to antigens•HUMORAL, i.e., antibodies

CELLS of the IMMUNE SYSTEM

• LYMPHOCYTES, T• LYMPHOCYTES, B• PLASMA CELLS (MODIFIED B CELLS)• MACROPHAGES, aka “HISTIOCYTES”, (APCs, i.e.,

Antigen Presenting Cells)• “DENDRITIC” CELLS (APCs, i.e., Antigen Presenting

Cells)

• NK (NATURAL KILLER) CELLS

GENERAL SCHEME ofCELLULAR EVENTS

• APCs (Macrophages, Dendritic Cells)• T-Cells (Control Everything)–CD4 “REGULATORS” (Helper)–CD8 “EFFECTORS”

• B-Cells Plasma Cells AB’s• NK Cells

The immune response

Immune response :It is a specific defense mechanism developing against particular types of irritants to overcome the irritant on subsequent exposure.

Hypersensitivity : Is the change in tissue reaction Following re- exposure to antigen

Def:Def:

IMMUNITY HYPERSENSITIVITY

When After first exposure Secondary exposure

Duration Take longer time Faster

Tissue damage No or minimal tissue damage

More tissue damage

LN More LN affection Less

Types InnateAdaptive

IIIIIIIV

Example

Type III(immune complex reaction)

Ag + Ab Immune complex with slight excess of Ag

Diffuse through the wall of blood vessels

Precipitate on the endothelial lining & outside blood vessels

Activation of complement Inflammatory reaction

With increase vascular permeability & exudation

Release of chemotactic factor PNL Phagocytose

complement & immune complex Proteolytic enzymes

Tissue destruction.

Types• @ Serum sickness• Oedema of the eye lid• Generalized lymphadenopathy• Urticaria• Fever & bone aches

• @ Arthus phenomenon• Repeated skin injection of the antigen (e.g. insulin)

tissue necrosis, hge. And ulceration

Systemic immune- complex disease

Acute serum sickness

Arthus reaction

1- Serum sickness2- Arthus reaction.3- Poly arteritis nodosa.4- Post streptococcal GN.5- SLE.

Examples

Serum sickness