IMMUNITY IMMUNITY Resistance exhibited by the host towards

IMMUNITY

IMMUNITY Resistance exhibited by the host towards injury caused by micro-organisms and their products Protection against infection consequence of Immune response one In true sense it is the reaction of body against any foreign Ag.

TYPES OF IMMUNITY Immunity Innate inborn genetic factors Specific, Nonspecific Acquired Active own Ab Species Race Individual Natural imm. to Artificial Infec. Agents Immunization Passive ready made Ab Natural Maternal Abs Artificial Abs from other sources

INNATE IMMUNITY Resistance inherited by virtue of its genetic and constitutional make up. Nothing to do with prior contact with micro-organisms or immunization. Nonspecific Specific pathogen. Resistance in general. Resistance against particular Species Immunity: - Total or relative refractoriness to a pathogen, shown by all member of species.

Species Immunity Contd. Human pathogens insusceptible to plant pathogens and vice versa and to many pathogens of animals. Racial Immunity: Within species, different races show difference in susceptibility to infection. Examples: - High resistance of Algerian sheep to anthrax - American Negroes are more susceptible to tuberculosis than American whites. - Sickle cell anemia confer immunity to malaria in some part of Africa.

Individual Immunity Individuals in single race exhibit different Immunity. Several factors influence the level of immunity. Genetic basis: Homozygous twin exhibit similar degree of resistance or susceptibility to Lepromatous leprosy or Tuberculosis. Age: Two extremes of life more susceptible to infection. Foetus placental barrier (Exceptions: TORCH)

Individual Immunity Suckling Mice susceptible to coxsackie virus Young people Tenia capitis (Microsp audonii) Pre-pubertal girl (Vag. Epithelium) Gonococci Adult Chicken pox Poliomyelitis

MECHANISM OF IMMUNITY A) Epithelial covering (Skin, mucus membrane) Protection against microbial invasion In addition to mechanical barrier, the bactericidal action is due to - High concentration of salt in dry sweat - Sebaceous secretion - Long chain fatty acids and soaps B) The mucosa of Resp. tract Very architecture of nose prevent entry of inhaled particles, arrested at the entry by cilia Cough reflex The nasal and resp. secretion contain mucopolysacchrides (neutralise Influenza and other viruses Particles at aleveoli are ingested by phagocytes.

Mouth is constantly bathed with saliva which have inhibition effect on micro-organism High acidity of stomach Particles get enmeshed in intestine and propelled by peristalsis Conjunctiva; Lysozyme cause lysis of bacteria Flushing action of urine Spermine and zinc (semen) Acidity of Adult vagina pathogen Anti bacterial Inhospitable for many

ANTI BACTERIAL SUBSTANCES Complement system, euglobin Properdine along with complement and Mg++ ions lysis of GM-ve Bacteria β – Lysin active against anthrax Basic polypeptide: Leukin from Leucocites, plakin (platelets) Lacticacid from muscle Spermine (kidney) killed TB bacilli & staph – Interferon (protection and recovery from viral infection Neuraminidase Inhibits viral Haemagglutin AC phase proteins (C-reacltive pr, 1 antitrypsin, 2 macroglobin, amyloid Pr, fibrinogen etc.

CELLULAR FACTORS Phagocytes: Blood Tissue Neutro, Eosino, Mono N. K Kupffer, Litoral, Alv Macro, Microglea Surface phagocytosis: Cap Bact. in presence of opsonins Killing of Bacteria: - Intracellular Neutro, Macro - Extra cellular Eosino, NK cells

INFLAMMATION Non specific mech. of defense Protective phenomenon - Fibrin barrier Limits infl. or infection - Dilution of toxins & enzymes - Phagocytosis (chemotactic factor, C 5 a, histamin Leukotriene etc. - Complement activation - Activation of specific defense.

FEVER Mobilises defences, accelerate repair and inhibits pathogens A rise of temp. Destroy organism Therapeutic induction of fever in syphilis

ACQUIRED IMMUNITY The resistance an individual acquires during life Active Immunity - Resistance in host in response to antigenic stimulus. Involves functioning of the individual immune system - Latent phase, Negative phase, Sec. response, Immunological memory.

Active (Natural) Clinical or sub clinical Recovery from small pox, measles. Adults have natural immunity against polio after repeated subclinical infection No immunity against common cold virus infection Anti bacterial immunity lasts shorter period Premunition: (Infection immunity) Immunity to reinfection lasts as long as original infection persists (Malaria, Syphilis).

Active (Artificial) Resistance produced, in the host by vaccines Vaccines Live or killed micro-organisms and their products used for immunization Bacterial vaccines: - Live (attenuated): BCG, B. anthracis, plague, Brucella (Avirulent, attenuated strains) - Killed (Inactivated): TAB, cholera, pertusis, Haemophilus, Pneumo, Meningo Bact. cap poly Viral vaccines: - Live (attenuated): Small pox, polio (sabin), MMR (measles, mumps, rubella), Influenza - Killed (Polio, salk), yellow fever, Rabies (flury) Influenza, JE (Japanese encephalitis) Bacterial products Toxoid of diphtheria and tetanus, Tripple vaccine (Toxoids + Bacteria).

Characteristics of Live and Killed vaccines Live vaccine: - Initiates infection without causing injury or disease - Immunity lasts for several years. Booster doses may be required - Given intradermally or orally. Oral vaccines produce local immunity or CMI Killed vaccine: - Less immunogenic. Booster doses always required - Immunity lasts for short period - Given parentrally. Produce AMI

PASSIVE IMMUNITY Resistance transferred to a recipient in ready made form. Preformed antibodies are introduced Passive (Natural): Resistance passively transferred from mothers to foetus and babies. - Maternal Ab through placenta to foetus - Colostrum rich in Ig A, Ig G from mother to infant.

PASSIVE (ARTIFICIAL) Resistance passively transferred by administration of antibody. - Hyper immune sera (ATS, ADS, AGS etc. ) - Convalescent sera from patients (measles, rubella) - Pooled gama globulin (against infectious diseases) - ALS (In transplantation surgery) - Rh- isoimmunization

Combined Immunization ATS + Toxoid (Road injury) Immunoglobulin + HDCV Post – expoprophy (rabies) Adoptive Immunity Injection of lymphocytes Transfer factor An extract obtained from immuno- competent lymphocytes (Leprosy, candidiasis, malignancy, multiple sclerosis).

Herd Immunity: Over all level of immunity in a community and is relevant in control of epidemic diseases (Diphtheria, poliomyetitis etc. ) Local Immunity: v It is the resistance produced at the local site preventing the entry and multiplication v Sabin (oral) vaccine (polio) influenza nasal spray v Secretory immunoglobulin (Igs A) plays important role preventing the entry at the primary site.

Active • Mechanism Host Imm. System Passive Obtained passively plays role • Induction By infection (clinical, subclin) Conferred by ready made Ab immunogens, vaccines • Durability Durable and effective Transient, less effective • Lag phase Present • Imm. Memory Present • Appl. To Imm. Not effective def. subject No lag phase No memory Effective