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Acquired Immunity

Acquired (Adaptive) Immunity Defensive mechanisms include : Defensive mechanisms include : 1) Innate immunity (Natural or Non specific) 1) Innate immunity (Natural or Non specific) 2) Acquired immunity (Adaptive or Specific ) 2) Acquired immunity (Adaptive or Specific ) Cell-mediated immunity Humoral immunity Cell-mediated immunity Humoral immunity

Aquired (specific) immunity * The acquired immune response is more specialized than innate immune response than innate immune response * The acquired immune response involves a combination of two mechanisms : of two mechanisms : 1) Humoral immune response 1) Humoral immune response 2) cell mediated immune response 2) 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) immunity Two mechanisms 1) Humoral immune response: - Antibodies are produced by B-lymphocytes - Antibodies are produced by B-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) - It is mediated by certain types of T-lymphocytes - It is mediated by certain types of T-lymphocytes - T-lymphocytes recognize foreign material by - T-lymphocytes recognize foreign material by means of surface receptors means of surface 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. cytokines i.e. cytokines

Characters Of Acquired Immune Response 1) Highly specific for the invading organism 2) Discrimination between “self and “non self” molecules The response only occurs to “non self” molecules The response only occurs to “non self” molecules 3) Diversity: - It can respond to millions of different antigens - It can respond to millions of different antigens - Lymphoctes population consists of many different clones (one cell and its progny) - Lymphoctes population consists of many different clones (one cell and its progny) - Each clone express an antigen receptor and responds only to one antigenic epitope - Each clone express an antigen receptor and responds only to one antigenic epitope

Mechanism Of Acquired Immune Response Acquired immune response is initiated by: Acquired immune response is initiated by: * Recognition of the antigen by specific lymphocytes * Activation of these specific lymphocytes * 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 re-exposure to same antigen

Acquired Or Adaptive Immunity I- Passive acquired immunity a-Naturally passive acquired immunity a-Naturally passive acquired immunity Antibodies are passed through placenta Antibodies are passed through placenta to the fetus to the fetus b- Artificially passive acquired immunity b- 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 immunity a-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 immunity : - Following vaccination with live or killed - Following vaccination with live or killed infectious agents or their products infectious agents or their products

Mechanism of Humoral immunity * Antibodies induce resistance through: 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 infection a- Previous infection b- Artificial immunization b- Artificial immunization c- Transferred passively as antiserum c- Transferred passively as antiserum * Neutralization of toxin with antitoxin prevents a combination with tissue cells

Mechanism of Humoral immunity 2) Antibodies attach to the surface of bacteria and a- act as opsonins and enhance phagocytosisd a- 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 gut their target cells, e.g. IgA in the gut c- Activate the complement and lead to bacterial lysis c- Activate the complement and lead to bacterial lysis d- Clump bacteria (agglutination) leading to d- Clump bacteria (agglutination) leading to phagocytosis phagocytosis

Vaccination * Vaccination prevents and control such diseases as cholera, rabies, poliomyelitis, diphtheria, tetanus, measles, and typhoid fever cholerarabiestyphoid fever cholerarabiestyphoid fever * Vaccines can be: a- (e.g. to prevent the effects a- prophylactic (e.g. to prevent the effectsprophylactic of a future infection by any natural or of a future infection by any natural orinfection "wild" pathogen "wild" pathogenpathogen b- Therapeupic (e.g. vaccines against cancer b- Therapeupic (e.g. vaccines against cancerherapeupic are also being investigated) are also being investigated)

Vaccination Vaccination: *Producing immunity against pathogens (viruses and bacteria) by the introduction of live, killed, or altered antigens that stimulate the body to produce antibodies against more dangerous forms *Producing immunity against pathogens (viruses and bacteria) by the introduction of live, killed, or altered antigens that stimulate the body to produce antibodies against more dangerous formsimmunity *Vaccines work with the immune system's ability to recognize and destroy foreign proteins (antigens) *Vaccines work with the immune system's ability to recognize and destroy foreign proteins (antigens)

Vaccination Immunization of young children and adolescents: - Hepatitis B (HepB) and Hepatitis A (HepA) - Diphtheria, tetanus and pertussis (whooping cough) given together as DTaP (formerly DTP) iphtheriatetanuswhooping coughiphtheriatetanuswhooping cough - Haemophilus influenzae b (Hib) - Poliomyelitis (IPV) oliomyelitis - Measles, Mumps, and Rubella, given together as MMR easlesumpsubellaeaslesumpsubella - Chicken pox (Var) hicken poxhicken pox - Neisseria meningitidis (meningococcal meningitis)

Cells Of Immune Response Cells involved in specific immune mechanisms are: I) Hematopoitic leucocytes 1- Lymphoid 1- Lymphoid * T-lymphocytes: * T-lymphocytes: - Antigen specific cells carrying CD 3 complex, CD 4, CD 8 - Antigen specific cells carrying CD 3 complex, CD 4, CD 8 - 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 Response * 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: - 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.) 2- Monocytic myeloid 2- 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.) 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.) ІІ-Non hematopoietic cells: - Dentritic cells - Dentritic cells - Astrocytes and - Astrocytes and - Endothelial cells - Endothelial cells Function : antigen presentation Function : antigen presentation

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