IMMUNITY AND IMMUNOLOGICAL PRPARATIONS

IMMUNITY AND IMMUNOLOGICAL PRPARATIONS

POINTS TO BE CONSIDERED:

1. Introduction to immunology

    a. Immunity

    b. Phagocytosis

    c. Antibody production

2. Types of Immunity

3. Terms used in immunity

4. Types of vaccines

    a. Simple

    b. Mixed

    c. Univalent

    d. Polyvalent

5. Classification of Immunological Preparation

    a. Preparation producing active immunity

    b. Diagnostic preparations containing bacterial toxins, used for Schick test and tuberculin test.

    c. Preparation containing antibodies used to produce passive immunity.

6. Storage of immunological products

1. INTRODUCTION TO IMMUNOLOGY:

Immunology is the study of immunity and preparations used to produce immunity are called immunological preparations. All immunological preparations are biological products which are administered parentally to avoid inactivation of the preparation on oral administration. Exception is poliomyelitis vaccine which is administered orally.

    a. IMMUNITY:

The infection or disease in human beings or animals is caused by the invasion of pathogenic microorganisms. The power of the body to resist the effects of invasion of pathogenic microorganisms is known as immunity. Factors responsible for immunity are:

   b. PHAGOCYTOSIS:

It can be defined as the ingestion of microbes by certain cells of the body whereby they are rendered harmless. It is caused by white blood cells and the cells of reticuloendothelial system.

   c. ANTIBODY PRODUCTION:

The body does not depend only on the process of phagocytosis for the destruction of pathogenic microbes. It produces other substances known as antibodies which destroy the pathogenic microorganism and their toxins. Hence, antibodies may be defined as substances produced in the body on invasion of pathogenic microbes either to destroy these pathogenic microbes or
their toxins.

2. TYPES OF IMMUNITY:

A. NATURAL/ INNATE/ NON-SPECIFIC IMMUNITY:

Innate immunity (also called nonspecific or natural immunity) refers to the inborn-ability of the body to resist, and is genetically transmitted from one generation to the next. This immunity offers resistance to any microorganism or foreign material encountered by the host.

It includes general mechanisms inherited as part of the innate structure and function of each vertebrate, and acts as first line of defense. Innate immunity lacks immunological memory, i.e., it

occurs to the same extent each time a microorganism or foreign material is encountered. Types of innate immunity:

a. Species immunity: (species resistance) is that in which a disease affecting one species does

not affect the other species. For convenience, humans do not contract cattle plague, chicken cholera, hog cholera, infectious horse anemia, etc., while animals are not affected by many human diseases such as enteric fever, scarlet fever, syphilis, gonorrhea, measles, etc.

b. Racial immunity: (racial resistance) is that in which various races (breeds) show marked

differences in their resistance to certain infectious diseases. A well-known example is that Brahman cattle are resistant to the protozoan parasite responsible for tick fever in other breeds of cattle.

c. Individual immunity: Having the same racial background and opportunity for exposure, some individuals of the race experience fewer or less severe infections than other individuals of the same race. For convenience, children are more susceptible to diseases such as measles and chicken pox, while aged individuals are susceptible to other diseases like pneumonia.

d. Age: Most of the children between 2-5 years of age group are susceptible to diphtheria whereas most adults are immune to it.

B. AQUIRED/SPECIFIC/ADAPTIVE IMMUNITY:

Acquired immunity (also called specific or adaptive immunity) refers to an immunity that is developed by the host in its body after exposure to a suitable antigen or after transfer of antibodies or lymphocytes from an immune donor.

a. ACTIVE IMMUNITY: In active immunity, there is active involvement of host’s own immune system leading to the synthesis of antibodies and/or the production of immuno-competent cells (ICCs). There are two types of active immunity:

i. NATURALLY ACQUIRED ACTIVE IMMUNITY: This immunity develops after antigens
(e.g., microbial pathogens) enter the body by natural processes such as infection and, in response, the body’s immune system forms antibodies. In some cases, the immunity may be life-long as with smallpox, measles, chickenpox, yellow fever etc. In other cases,

however, the immunity may be lost after only a few years (e.g., diphtheria, tetanus) or even for lesser period (e.g., influenza, pneumonia).

ii. ARTIFICIALLY ACQUIRED ACTIVE IMMUNITY: When a carefully chosen antigen (e.g., vaccine, chemically altered toxins called toxoids) is intentionally introduced into a body to be immunized, the latter develops immunity that is called artificially acquired active immunity. This immunity is artificial because the antigens are intentionally or purposely introduced, and it is active because the recipient’s immune system synthesizes antibodies in response. Vaccines provide usually long-term immunity. Vaccines are now available against many infectious diseases such as cholera, tuberculosis, plague, pneumonia, rocky mountain spotted fever, smallpox, polio, tetanus, influenza, measles, rabies, yellow fever etc. Toxoids are currently available for protection against diphtheria and tetanus, the two diseases whose major effects are due to toxins.

b. PASSIVE IMMUNITY: In passive immunity, on the contrary, the antibodies and /or the immuno-competent cells (ICCs) are transferred from one host to another. There are two types of passive immunity:

i. NATURALLY ACQUIRED PASSIVE IMMUNITY: When antibodies produced in the body of an individual (called “donor”) are naturally transferred into the body of other individual (called “recipient”), the latter develops immunity, called naturally acquired passive immunity, in its immune system. This immunity is natural because the transfer of antibodies from donor to recipient occurs under natural conditions, and it is passive because the recipient does not synthesize antibodies but picks them up from the donor. The best example of this type of immunity is the natural transfer of antibodies from the mother to the foetus across- the placenta. Certain antibodies are also transferred from mother to infant through colostrum and milk during nursing.

ii. ARTIFICIALLY ACQUIRED PASSIVE IMMUNITY: Artificially acquired passive immunity is that which develops as a result of the intentional introduction of antibody-rich serum (blood plasma devoid of clotting factors) taken from diseased individual to another susceptible individual. It was an important therapeutic device for disease treatment before the vaccines were developed and is still used for viral diseases such as hepatitis B, chicken pox, arthropod-borne encephalitis, and for bacterial diseases such as botulism, diphtheria, tetanus, staphylococcal-poisoning where toxins are involved in disease causation

3. TERMS USED IN IMMUNITY:

i. PATHOGENS: These are the infection causing microorganisms.

ii. ANTIGENS: these are the substances which stimulate the body to produce antibodies.

iii. TOXINS: These are poisonous substances produced by pathogenic microbes and lead to infections.

iv. EXOTOXINS: These are the toxins which can diffuse freely through the bacterial cell wall into the blood or medium in which they are growing.

v. ENDOTOXINS: These toxins cannot diffuse freely and released when the bacterial cell dies.

vi. ANTITOXINS: Substances containing antibodies which acts against exotoxins and endotoxins.

vii. SERA OR IMMUNE SERA: It is a clear liquid which separates from blood when it clots it is called serum. When a serum contains antitoxin antibodies it is known as antitoxic serum.

viii. TOXOIDS: These are the toxins whose toxicity has been removed by treating them with heat or chemicals but their antigenic properties are retained.

ix. VACCINES: These are the substances which are administered in the body to produce resistance against infectious diseases. They are mainly used as prophylactic treatment. Vaccines may contain living, attenuated or killed bacteria, viruses or rickettsia.

4. TYPES OF VACCINES

a. SIMPLE: These vaccines contains only one species of microorganisms.

b. MIXED: These vaccines contain two or more than two species of micro-organisms

c. UNIVALENT: These vaccines contains only one strain of a species.

d. POLYVALENT: These vaccines contains two or more strains of a species.

5. CLASSIFICATION OF IMMUNOLOGICAL PREPARATION

a. PREPARATION PRODUCING ACTIVE IMMUNITY:

i. Vaccine containing living bacteria e.g. BCG (Bacillus Calmette Guerin) vaccine: It is prepared by growing the bacteria in a suitable environment in sterile conditions and the antigenicity of the vaccine is maintained.

It is used as an immunizing agent against tuberculosis.

ii. Vaccine containing dead bacteria e.g. cholera vaccine: It is a sterile preparation of killed strains of Cholera vibrio in sodium chloride inj. Suspension is heated and sterilized in sterile vials and sealed immediately.

It is used for immunizing against cholera, it is effective for 3-6 months and is given by I.M or
S.C route.

iii. Vaccines containing killed rickettsia e.g. typhus vaccine: It is a suspension of killed typhus rickettsia. It is prepared in isotonic diluents and is stored in sterile containers under aseptic conditions.

It is used for immunization against disease and infections caused by rickettsia.

iv. Vaccines containing living virus e.g. measles: This vaccine is of two types, vaccine containing live virus and vaccines containing dead virus. These vaccines are prepared similar to that of poliomyelitis vaccine.

It is used by injection for prophylaxis of measles.

v. Vaccines containing toxoids e.g. tetanus vaccine: It is prepared from tetanus toxin produced by the growth of Clostridium tetni on a suitable culture medium.

It is used for active immunization against tetanus.

b. DIAGNOSTIC PREPARATIONS CONTAINING BACTERIAL TOXINS, USED FOR
SCHICK TEST AND TUBERCULIN TEST: these preparations are used to:

i. To identify whether an individual is immune to particular infection.

ii. To determine whether a useful degree of protection has been provided or not after immunization.

iii. To indicate whether particular disease is present in an individual or not

The following preparations are used for diagnostic purposes and their use is that they help to detect infections such as tuberculosis and diphtheria:

· Schick test toxin

· Schick control

· Old tuberculin

· Tuberculin purified protein derivatives

c. PREPARATION CONTAINING ANTIBODIES USED TO PRODUCE PASSIVE
IMMUNITY: these preparations are obtained from other microbes by inducing infection in them and the the antibodies prepared by their bodies are collected for human use. For e.g Diphtheria antitoxin, Botulin antitoxin, Tetanus antitoxin etc.

Antibacterial sera are used to provide passive immunity for disease caused by endotoxin producing bacteria. They were used against a no. of diseases such as typhoid, pneumonia etc. but now are replaced by chemotherapeutic agents.

Antiviral sera, Rabies antiserum, Measles serum etc. are other examples of preparation containing antibodies used to produce passive immunity.

6. STORAGE OF IMMUNOLOGICAL PRODUCTS:

Immunological products lose their therapeutic ability on storage due to denaturation of the proteins. High temperatures are directly proportional to the loss of activity of the products. Hence must be stored at temp between 2-10 degree Celsius.