Application of Immunology

• Clinical diagnosis • Treatment• Prophylaxis• Research

Types of immunity

• (Natural or Innate immunity)• (adaptive or acquired immunity)

Innate immunity

• First line of defence• Cellular and biochemical mechanisms are present before

infection• These mechanisms react only to microbes• They respond in essentially the same way to repeated

infections• The principal components of innate immunity are:a) Physical and chemical barriersb) Phagocytic cellsc) Blood proteins(CRP,complement,interferons)d) cytokines

Innate immunity

• Some components are functioning at all times even before infection

• Others are normally inactive but poised to respond rapidly to the microbes

Anatomical Barriers - Mechanical Factors

System or OrganCell typeMechanism

SkinSquamous epitheliumPhysical barrierDesquamation

Mucous Membranes

Non-ciliated epithelium (e.g. GI tract)

Peristalsis

Ciliated epithelium (e.g. respiratory tract)

Mucociliary elevator

Epithelium (e.g. nasopharynx)

Flushing action of tears, saliva, mucus, urine

Anatomical Barriers - Chemical Factors

System or OrganComponentMechanism

SkinSweatAnti-microbial fatty acids

Mucous Membranes

HCl (parietal cells)Tears and saliva

Low pHLysozyme and phospholipase A

Defensins (respiratory & GI tract)

Antimicrobial

Sufactants (lung)Opsonin

Anatomical Barriers - Biological Factors

System or OrganComponentMechanism

Skin and mucous membranes

Normal floraAntimicrobial substancesCompetition for nutrients and colonization

Humoral ComponentsComponentMechanism

ComplementLysis of bacteria and some virusesOpsoninIncrease in vascular permeabilityRecruitment and activation of phagocytic cells

Coagulation system

Increase vascular permeabilityRecruitment of phagocytic cellsΒ-lysin from platelets – a cationic detergent

Lactoferrin and transferrin

Compete with bacteria for iron

LysozymeBreaks down bacterial cell walls

CytokinesVarious effects

Cellular Components

CellFunctions

NeutrophilsPhagocytosis and intracellular killingInflammation and tissue damage

MacrophagesPhagocytosis and intracellular killingExtracellular killing of infected or altered self targetsTissue repairAntigen presentation for specific immune response

NK and LAK cellsKilling of virus-infected and altered self targets

EosinophilsKilling of certain parasites

interferon

• Type I(IFN-α,IFN-β) all immune cells and fibroblasts as an anti virus

• Type II(IFN- )

T cells as a immunoregulator

interferons

• Interferon alphas are used for treating cancers and viral infections

• interferon betas are used for treating multiple sclerosis

• interferon gamma is used for treating chronic granulomatous disease.

Adaptive immunity

• Stimulated by exposure to infectious and noninfectious agents,increase in magnitude and defensive capabilities with each succesive exposure to a particular microbe.

Types of adaptive immunity

• Humoral immunity (antibodies)Principal defence mechanism

against extracellular microbes and their toxins

• Cell mediated immunity (CMI)Defence against intracellular

microbes

Phases of adaptive immune resposes

• Recognition of antigen• Activation of lymphocytes• Elimination of antigen(effector

phase)• Decline of immune

responses(homeostasis)