IMMUNITY
The term Immunity is derived from the Latin word Immunitae, which referred to the protection from the legal prosecution offered to Roman Senators during their tenure in office. Refers to the resistance exhibited by the host towards injury caused by microorganisms and their products.
Protection against infectious diseases
Distinguishes self from non-self
Eliminate potentially destructive foreign substances from body
INNATE IMMUNITY
Resistance to infection which individual possesses by virtue of his genetic and constitutional make up Early defense response against microbes Immune response Non specific Innate response do not alter on repeated exposure Memory effect absent Not affected by immunisation or prior contact
ACQUIRED IMMUNITY
The resistance that an individual acquires during life Later defense response Immune response is highly specific Adaptive response improves with each successive encounter with same pathogen Memory effect present Is improved by immunisation
Species immunity
Refers to the total or relative refractoriness to a pathogen, shown by all members of species.
Person obtains by virtue of being a part of the human species. Determines whether or not a pathogen can multiply in them. For e.g. All human beings are totally unsusceptible to plant pathogens and to, many animal pathogens, such as render pest or distemper.
Pasteur’s experiments on anthrax in frogs, which are naturally resistant to the disease but become susceptible when their body temperature is raised from 25° to 35°C.
Racial immunity
Racial differences are known to be genetic in origin For e.g.
People of Negroid origin in USA are more susceptible than the Caucasians to tuberculosis.
Genetic resistance to Plasmodium falciparum Malaria seen in some parts of Africa and Mediterranean coast. A hereditary abnormality of red cells (sickling) prevalent in the area, confer immunity to infections by malarial parasite.
Individual immunity
The difference in innate immunity exhibited by different individuals in a race
The genetic basis of individual immunity is seen in twins. For e.g. Homozygous twins exhibit similar degrees of resistance or susceptibility to Lepromatous leprosy and Tuberculosis.
Innate immunity does not recognize every possible antigen instead it recognizes pathogen-associated molecular patterns. Receptors enable the phagocyte to attach to these patterns so it can be engulfed and destroyed by lysosomes.
Pathogen-Associated Molecular Patterns Binding to Endocytic PatternRecognition Receptors on Phagocytes
Determinants of innate immunity
I. Species and strains
II. Age
III. Hormonal Influences
IV. Nutrition
MECHANISMS OF INNATE IMMUNITY
I. Epithelial surfaces Skin Mucosa of the respiratory tract Human eye. Flushing action of urine
II. Antibacterial substances in Blood and tissues
III. Inflammation
IV. Fever
V. Cellular factors
ACQUIRED IMMUNITY
A person is said to be immune when he possesses specific protective antibodies or cellular immunity as a result of previous infection or immunization or is so conditioned by such previous experience as to respond adequately to prevent infection Because this form of immunity develops as a response to infection and is adaptive to the infection, it is called adaptive immunity.
The characteristics of adaptive immunity are
Specificity for distinct molecules.
An ability to remember and respond more vigorously to repeated exposure to the same microbe. Hence it is also called as specific immunity.
ACTIVE IMMUNITY
1. Produced actively by host’s immune system
2. Induced by infection or by contact with immunogens (vaccines, allergens etc).
3. Affords desirable and effective protection
4. Immunity effective only after a lag period (time required for generation of antibodies).
5. Immunological memory present; subsequent challenge more effective (booster effect)
6. Negative phase may occur
7. Not applicable in immunodeficient hosts
PASSIVE IMMUNITY
1. Received passively by the host
2. No participation by the host’s immune system
3. Conferred by introduction of readymade antibodies
4. Protection transient and less effective Immunity effective immediately
5. No immunological memory subsequent administration of antibodies less effective due to immune elimination
6. No negative phase
7. Applicable in immunodeficient hosts
Natural Active immunity
This results from either a clinical or inapparent infection.
Immunity following chicken pox and measles infection is usually life long Artificial Active Immunity
This is the resistance induced by vaccines.
Vaccines are preparations of live or killed microorganisms or their products used for immunization.
Types of Vaccine:
Immunizing agents that are used for immunoprophylaxis
Bacterial vaccines: Live (BCG vaccine for T.B.).
Killed (Cholera vaccine).
Subunit (Typhoid Vi antigen).
Bacterial products (Tetanus Toxoid).
Viral Vaccine: Live (Oral polio vaccine – Sabin).
Killed (Injectable polio vaccine – Salk).
Subunit (Hepatitis B-vaccine).
Combinations If more than one kind of immunizing agent is included in the vaccine, it is called a mixed or combined vaccine.
DPT (Diphtheria – pertussis - tetanus)
MMR (Measles, mumps and rubella).
DPTP (DPT plus inactivated polio).
Natural Passive immunity
This is the resistance passively transferred from the mother to the baby. In human infants, maternal antibodies are transmitted predominantly through the placenta.
Human colustrum, which is also rich in IgA antibodies and resistant to intestinal digestion.
Synthesis of antibodies (IgM) occurs at 20th week of IUL but its immunogenic capacity is still inadequate at birth. It is only by about the age of three month that the infants acquire a satisfactory level of immunological independence.
Artificial passive immunity
This is the resistance passively transferred to a recipient by administration of antibodies.
Passive immunization is indicated for immediate and temporary protection in a non-immune host
Employed for the suppression of active immunity, when the latter may be injurious. Used as treatment of some infections.
Hyper immune sera of animal or human origin, convalescent sera and pooled human gamma globulins are used for prophylaxis and therapy. Rh immune globulin is used during delivery to prevent immune response to the Rhesus factor in Rh-negative women with Rh-positive babies.
Cells of the Innate Immune System: Phagocytes Macrophages play several roles in the immune responses:
Phagocytosis.
Required to process and present antigen to immunocompetent T cells for induction of CMI.
Production of cytokines, such as IL-1 and TNFα, which are proinflammatory
Lyses tumor cells by secreting toxic metabolites and proteolytic enzymes
Examples of tissue macrophages are kuppfer cell of the liver, microglial cells of brain, mesangial phagocyte of the kidney, alveolar macrophages of lungs and osteoclasts of bone.
The term Immunity is derived from the Latin word Immunitae, which referred to the protection from the legal prosecution offered to Roman Senators during their tenure in office. Refers to the resistance exhibited by the host towards injury caused by microorganisms and their products.
Protection against infectious diseases
Distinguishes self from non-self
Eliminate potentially destructive foreign substances from body
INNATE IMMUNITY
Resistance to infection which individual possesses by virtue of his genetic and constitutional make up Early defense response against microbes Immune response Non specific Innate response do not alter on repeated exposure Memory effect absent Not affected by immunisation or prior contact
ACQUIRED IMMUNITY
The resistance that an individual acquires during life Later defense response Immune response is highly specific Adaptive response improves with each successive encounter with same pathogen Memory effect present Is improved by immunisation
Species immunity
Refers to the total or relative refractoriness to a pathogen, shown by all members of species.
Person obtains by virtue of being a part of the human species. Determines whether or not a pathogen can multiply in them. For e.g. All human beings are totally unsusceptible to plant pathogens and to, many animal pathogens, such as render pest or distemper.
Pasteur’s experiments on anthrax in frogs, which are naturally resistant to the disease but become susceptible when their body temperature is raised from 25° to 35°C.
Racial immunity
Racial differences are known to be genetic in origin For e.g.
People of Negroid origin in USA are more susceptible than the Caucasians to tuberculosis.
Genetic resistance to Plasmodium falciparum Malaria seen in some parts of Africa and Mediterranean coast. A hereditary abnormality of red cells (sickling) prevalent in the area, confer immunity to infections by malarial parasite.
Individual immunity
The difference in innate immunity exhibited by different individuals in a race
The genetic basis of individual immunity is seen in twins. For e.g. Homozygous twins exhibit similar degrees of resistance or susceptibility to Lepromatous leprosy and Tuberculosis.
Innate immunity does not recognize every possible antigen instead it recognizes pathogen-associated molecular patterns. Receptors enable the phagocyte to attach to these patterns so it can be engulfed and destroyed by lysosomes.
Pathogen-Associated Molecular Patterns Binding to Endocytic PatternRecognition Receptors on Phagocytes
Determinants of innate immunity
I. Species and strains
II. Age
III. Hormonal Influences
IV. Nutrition
MECHANISMS OF INNATE IMMUNITY
I. Epithelial surfaces Skin Mucosa of the respiratory tract Human eye. Flushing action of urine
II. Antibacterial substances in Blood and tissues
III. Inflammation
IV. Fever
V. Cellular factors
ACQUIRED IMMUNITY
A person is said to be immune when he possesses specific protective antibodies or cellular immunity as a result of previous infection or immunization or is so conditioned by such previous experience as to respond adequately to prevent infection Because this form of immunity develops as a response to infection and is adaptive to the infection, it is called adaptive immunity.
The characteristics of adaptive immunity are
Specificity for distinct molecules.
An ability to remember and respond more vigorously to repeated exposure to the same microbe. Hence it is also called as specific immunity.
ACTIVE IMMUNITY
1. Produced actively by host’s immune system
2. Induced by infection or by contact with immunogens (vaccines, allergens etc).
3. Affords desirable and effective protection
4. Immunity effective only after a lag period (time required for generation of antibodies).
5. Immunological memory present; subsequent challenge more effective (booster effect)
6. Negative phase may occur
7. Not applicable in immunodeficient hosts
PASSIVE IMMUNITY
1. Received passively by the host
2. No participation by the host’s immune system
3. Conferred by introduction of readymade antibodies
4. Protection transient and less effective Immunity effective immediately
5. No immunological memory subsequent administration of antibodies less effective due to immune elimination
6. No negative phase
7. Applicable in immunodeficient hosts
Natural Active immunity
This results from either a clinical or inapparent infection.
Immunity following chicken pox and measles infection is usually life long Artificial Active Immunity
This is the resistance induced by vaccines.
Vaccines are preparations of live or killed microorganisms or their products used for immunization.
Types of Vaccine:
Immunizing agents that are used for immunoprophylaxis
Bacterial vaccines: Live (BCG vaccine for T.B.).
Killed (Cholera vaccine).
Subunit (Typhoid Vi antigen).
Bacterial products (Tetanus Toxoid).
Viral Vaccine: Live (Oral polio vaccine – Sabin).
Killed (Injectable polio vaccine – Salk).
Subunit (Hepatitis B-vaccine).
Combinations If more than one kind of immunizing agent is included in the vaccine, it is called a mixed or combined vaccine.
DPT (Diphtheria – pertussis - tetanus)
MMR (Measles, mumps and rubella).
DPTP (DPT plus inactivated polio).
Natural Passive immunity
This is the resistance passively transferred from the mother to the baby. In human infants, maternal antibodies are transmitted predominantly through the placenta.
Human colustrum, which is also rich in IgA antibodies and resistant to intestinal digestion.
Synthesis of antibodies (IgM) occurs at 20th week of IUL but its immunogenic capacity is still inadequate at birth. It is only by about the age of three month that the infants acquire a satisfactory level of immunological independence.
Artificial passive immunity
This is the resistance passively transferred to a recipient by administration of antibodies.
Passive immunization is indicated for immediate and temporary protection in a non-immune host
Employed for the suppression of active immunity, when the latter may be injurious. Used as treatment of some infections.
Hyper immune sera of animal or human origin, convalescent sera and pooled human gamma globulins are used for prophylaxis and therapy. Rh immune globulin is used during delivery to prevent immune response to the Rhesus factor in Rh-negative women with Rh-positive babies.
Cells of the Innate Immune System: Phagocytes Macrophages play several roles in the immune responses:
Phagocytosis.
Required to process and present antigen to immunocompetent T cells for induction of CMI.
Production of cytokines, such as IL-1 and TNFα, which are proinflammatory
Lyses tumor cells by secreting toxic metabolites and proteolytic enzymes
Examples of tissue macrophages are kuppfer cell of the liver, microglial cells of brain, mesangial phagocyte of the kidney, alveolar macrophages of lungs and osteoclasts of bone.
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