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Acquired ImmunityAcquired Immunity

Acquired (Adaptive) ImmunityAcquired (Adaptive) Immunity

Defensive mechanisms include :Defensive mechanisms include : 1) Innate immunity 1) Innate immunity (Natural or Non specific) (Natural or Non specific) 2) Acquired immunity 2) Acquired immunity (Adaptive or Specific(Adaptive or Specific))

Cell-mediated immunity Humoral immunityCell-mediated immunity Humoral immunity

Aquired (specific) immunityAquired (specific) immunity

* The * The acquiredacquired immune response is immune response is moremore specializedspecialized than than innateinnate immune response immune response

* The acquired immune response involves a combination* The acquired immune response involves a combination of two mechanisms :of two mechanisms : 1) Humoral immune response1) Humoral immune response

2) cell mediated immune response2) cell mediated immune response

* They interact with one another to destroy foreign body* They interact with one another to destroy foreign body (microorganisms, infected cells, tumor cells)(microorganisms, infected cells, tumor cells)

Aquired (specific) immunityAquired (specific) immunityTwo mechanismsTwo mechanisms1) Humoral immune response:1) Humoral immune response: - - AntibodiesAntibodies are produced by are produced by B-lymphocytesB-lymphocytes - These have the ability to recognize and bind - These have the ability to recognize and bind specifically to antigen that induced their formation specifically to antigen that induced their formation

2) The cell mediated immune response (CMI)2) The cell mediated immune response (CMI) - It is mediated by certain types of - It is mediated by certain types of T-lymphocytesT-lymphocytes - T-lymphocytes recognize foreign material by - T-lymphocytes recognize foreign material by means of means of surface receptorssurface receptors - T-lymphocytes attack and destroy foreign material - T-lymphocytes attack and destroy foreign material directly or through release of soluble mediators directly or through release of soluble mediators i.e. i.e. cytokinescytokines

Characters Of Acquired Immune ResponseCharacters Of Acquired Immune Response

1) Highly specific1) Highly specific for the invading organism for the invading organism

2) Discrimination between “self and “non self” molecules2) Discrimination between “self and “non self” molecules The response only occurs to “non self” moleculesThe response only occurs to “non self” molecules

3) Diversity:3) Diversity: - It can respond to millions of different antigens- It can respond to millions of different antigens - Lymphoctes population consists of many different - Lymphoctes population consists of many different

clones (one cell and its progny)clones (one cell and its progny) - Each clone express an antigen receptor and responds - Each clone express an antigen receptor and responds

only to one antigenic epitopeonly to one antigenic epitope

Mechanism Of Acquired Immune ResponseMechanism Of Acquired Immune Response Acquired immune response is initiated by:Acquired immune response is initiated by:

* Recognition of the antigen by specific lymphocytes* Recognition of the antigen by specific lymphocytes

* Activation of these specific lymphocytes* Activation of these specific lymphocytes

* Proliferation and differentiation into effector cells;* Proliferation and differentiation into effector cells;

-The effector cells eliminate the antigen-The effector cells eliminate the antigen

-Return of homeostasis and development of memory cells-Return of homeostasis and development of memory cells

* Memory cells evoke a more rapid and long response on * Memory cells evoke a more rapid and long response on re-exposure to same antigenre-exposure to same antigen

Acquired Or Adaptive ImmunityAcquired Or Adaptive Immunity

I- Passive acquired immunityI- Passive acquired immunity a-Naturally passive acquired immunitya-Naturally passive acquired immunity Antibodies are passed through placenta Antibodies are passed through placenta to the fetusto the fetus

b- Artificially passive acquired immunityb- Artificially passive acquired immunity The injection of alredy prepared antibodies, The injection of alredy prepared antibodies,

such as gamma globulin such as gamma globulin (short-term immunization)(short-term immunization)

II- Active acquired immunityII- Active acquired immunity

a-Natural active acquired immunitya-Natural active acquired immunity : : - Following clinical or subclinical infections- Following clinical or subclinical infections - measles or mumps, in which immunity is - measles or mumps, in which immunity is long lasting long lasting b- Artificial active acquired immunityb- Artificial active acquired immunity : : - - Following vaccination with live or killed Following vaccination with live or killed infectious agents or their productsinfectious agents or their products

Mechanism of Humoral immunityMechanism of Humoral immunity* Antibodies induce resistance through:* Antibodies induce resistance through:

1) Antitoxin neutralize bacterial toxins (diphtheria,tetanus)1) Antitoxin neutralize bacterial toxins (diphtheria,tetanus) Antitoxin are developed actively as a result of: Antitoxin are developed actively as a result of: a- Previous infectiona- Previous infection b- Artificial immunizationb- Artificial immunization c- Transferred passively as antiserumc- Transferred passively as antiserum * Neutralization of toxin with antitoxin prevents a * Neutralization of toxin with antitoxin prevents a

combination with tissue cells combination with tissue cells

Mechanism of Humoral immunityMechanism of Humoral immunity2) Antibodies attach to the surface of bacteria and2) Antibodies attach to the surface of bacteria and a- act as opsonins and enhance phagocytosisda- act as opsonins and enhance phagocytosisd b- prevent the adherence of microorganisms to b- prevent the adherence of microorganisms to their target cells, e.g. IgA in the guttheir target cells, e.g. IgA in the gut c- Activate the complement and lead to bacterial lysisc- Activate the complement and lead to bacterial lysis d- Clump bacteria (agglutination) leading to d- Clump bacteria (agglutination) leading to phagocytosisphagocytosis

VaccinationVaccination* Vaccination* Vaccination prevents and control prevents and control such diseases as such diseases as

choleracholera, , rabiesrabies, poliomyelitis, diphtheria, tetanus, , poliomyelitis, diphtheria, tetanus, measles, and measles, and typhoid fevertyphoid fever

* Vaccines can be:* Vaccines can be: a- a- prophylactic (e.g. to prevent the effects (e.g. to prevent the effects of a future of a future infectioninfection by any natural or by any natural or "wild" "wild" pathogenpathogen

b- b- TTherapeupicherapeupic (e.g. vaccines against cancer (e.g. vaccines against cancer are also being investigated)are also being investigated)

VaccinationVaccinationVaccination:Vaccination: *Producing *Producing immunityimmunity against pathogens against pathogens

(viruses and bacteria) by the introduction of (viruses and bacteria) by the introduction of live, killed, or altered antigens that stimulate live, killed, or altered antigens that stimulate the body to produce antibodies against more the body to produce antibodies against more dangerous forms dangerous forms

*Vaccines work with the immune system's *Vaccines work with the immune system's ability to recognize and destroy foreign ability to recognize and destroy foreign proteins (antigens)proteins (antigens)

VaccinationVaccinationImmunization of young children and adolescents:Immunization of young children and adolescents: - - Hepatitis BHepatitis B (HepB) and (HepB) and Hepatitis AHepatitis A (HepA) (HepA) - - DDiphtheriaiphtheria, tetanus and pertussis , tetanus and pertussis (whooping cough) (whooping cough)

given together as DTaP (formerly DTP)given together as DTaP (formerly DTP) - - Haemophilus influenzae bHaemophilus influenzae b (Hib) (Hib) - - PoliomyelitisPoliomyelitis (IPV) (IPV) - - Measles, Mumps, and RubellaMeasles, Mumps, and Rubella, given together as , given together as MMRMMR - - Chicken poxChicken pox (Var) (Var) - - Neisseria meningitidisNeisseria meningitidis (meningococcal meningitis) (meningococcal meningitis)

Cells Of Immune ResponseCells Of Immune ResponseCells involved in specific immune mechanisms are:Cells involved in specific immune mechanisms are:

I) Hematopoitic leucocytesI) Hematopoitic leucocytes 1- Lymphoid1- Lymphoid * T-lymphocytes:* T-lymphocytes: - Antigen specific cells carrying - Antigen specific cells carrying CDCD33 complex, CD complex, CD44, CD, CD88 - Dominant blood lymphocytes (70%)- Dominant blood lymphocytes (70%) - Produce cytokines- Produce cytokines - Activation of other cells (Th CD4) - Activation of other cells (Th CD4) - Suppressors for others (Ts CD8)- Suppressors for others (Ts CD8)

Cells Of Immune ResponseCells Of Immune Response

* B-lymphocytes:* B-lymphocytes: - Antigen specific cells with surface receptor- Antigen specific cells with surface receptor - Less common lymphocytes (20%)- Less common lymphocytes (20%) - Responsible for antibody production- Responsible for antibody production

* NK, K cells:* NK, K cells: -- Not antigen specific Not antigen specific - Carry Fc receptors , NK-target cell receptor- Carry Fc receptors , NK-target cell receptor

Cells of Immune Response (cont.)Cells of Immune Response (cont.) 2- Monocytic myeloid2- Monocytic myeloid

a- Monocyte-tissue macrophages:a- Monocyte-tissue macrophages: . Non specific. Non specific . Carry Fc receptors. Carry Fc receptors . Phagocytic. Phagocytic . Antigen processing and presenting cells. Antigen processing and presenting cells . Produce cytokines. Produce cytokines

b- Neutrophils:b- Neutrophils: . Non specific. Non specific . Carrying Fc, complement molecules. Carrying Fc, complement molecules

Cells of Immune Response (cont.)Cells of Immune Response (cont.)

c- Eosinophils:c- Eosinophils: . Non specific. Non specific . Carrying Fc receptor. Carrying Fc receptor . Produce allergic mediators. Produce allergic mediators

d- Basophils and Mast cells:d- Basophils and Mast cells: . Non specifc. Non specifc . Carrying Fc receptors. Carrying Fc receptors . Produce allergic mediators. Produce allergic mediators

Cells of Immune Response (cont.)Cells of Immune Response (cont.)

ІІІІ-Non hematopoietic cells:-Non hematopoietic cells: - Dentritic cells- Dentritic cells - Astrocytes and - Astrocytes and - Endothelial cells- Endothelial cells

Function :Function : antigen presentation antigen presentation

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