Factors affecting antibody production

• Antibodies, which are also called immunoglobulin, are proteins which are protective in nature.
• Usually  produced by the immune system in response to the presence of a foreign substances that can be bacteria, virus, fungi or any other living forms.
• There are various factors affecting antibody production. They are as follows:

a) Age

• The embryo is immunologically immature.
• But it starts showing some degree of immune response at about 5 months of gestation with the development and differentiation of lymphoid organs.
• Rapid improvement is seen after birth in immune response and this response continues to improve at least up to the age of one year.
• However, full immune-competence is acquired at about the age of four years.

b) Genetic factor

• Immune response is under the control of Ir (MHC class II) genes.
• Due to genetic factor, response to same antigen in different individuals varies.
• Responders are those persons who are capable of responding to a particular antigen whereas those who are unable to respond are non-responder.

c) Nutritional status

• If there is protein calorie malnutrition, immune response is suppressed.
• Also the deficiency in amino acids like (tryptophan, phenyl alanine, methionine, glycine) and some vitamins (A, B, folic acid), immune response will be slow.

d) Dose of antigen

• An antigen is immunogenic only when administered above a minimal critical dose.
• Antibody production cannot be stimulated if there is very small dose of antigen and also very large dose inhibit antibody production.
• This condition is known as immunological paralysis.
• With secondary antigenic stimulus, there is increased antibody response.

e) Route of administration

• Parenteral administration of antigen shows better humoral immune response than oral or nasal routes.
• However, for IgA production, oral and nasal routes are also suitable and inhalation of pollen antigens induces IgE production.

f) Multiple antigens

• With simultaneous administration of two or more antigens, antibody response to one or other of the antigens may be enhanced as in triple vaccine (diphtheria, tetanus, pertussis), or diminished (antigenic competition).

g) Adjuvants

• Adjuvants are those substances which enhances the production of antibody when injected together with antigen.
• They are prepared as in water in oil emulsion (an aqueous solution of an antigen emulsified in a light mineral oil).
• In this emulsion, tiny drops of antigen are uniformly distributed throughout the oil.
• On injection of adjuvant mixed antigen, depots of antigen are formed from which soluble antigen is slowly released.
• This prolongs the antigenic stimulus.
• Both primary and secondary immune responses develop with as single dose of adjuvant mixed vaccine.
• Freund’s adjuvant is the most potent and widely used.

Types of adjuvants

• Depot: alum, aluminium hydroxide or phosphate and Freund’s incomplete adjuvant (water in arachis oil).
• Bacterial: Freund’s complete adjuvant contains water in arachis oil and dead mycobacteria.
• Chemical: silica particles, beryllium sulphate, bentonite and calcium alginate.

 Action of adjuvants

• Sustained release of antigen from depot.
• Liberation of lymphocyte activating factor.
• Lymphocyte stimulation- B, T cell or both.
• Anti-tumour effect by stimulating specific CMI.

h) Immuno-suppressive agents

• These agents inhibit immune response.
• X-irradiation, radiomimetic drugs (alkylating agents), corticosteroids, antimetabolites and anti-lymphocyte serum are some commonly used agents.
• X-ray and alkylating agents (cyclophosphamide, nitrogen mustard) when administered 2-3 days after administration of antigen, there is complete suppression of the antibody response.

Image source: cjasn 

1. Corticosteroids

• They cause depletion of lymphocytes from the blood and lymphoid tissues when administered in high dose.
• Therapeutic dose has got no inhibitory effect on immune response.

2. Anti-metabolites

• Folic acid antagonists (methotrexate), analogues of purine (6-mercaptopurine, azathioprine), cytosine arabinoside, and uracil (5- fluorouracil) interfere with synthesis of DNA, RNA or both.
• This inhibits cell division and differentiation necessary for humoral and cellular immune response.
• Cyclosporine is widely employed in immune-suppression nowadays.
• It has got neither any cytotoxic effect on lymphocytes nor any antimitotic activity but selectively inhibits helper T- cell activity.

3. Anti-lymphocytic serum (ALS)

• A heterologous antiserum raised against lymphocytes or thymocytes, is devoid of undesirable side effects except on lymphocytes.
• ALS for human use is produced in horses.
• IgG is active in ALS and IgM is inactive.
• The substance is effective primarily against T- lymphocytes and specifically on cell mediated immunity.
• Humoral immune response to thymus-independent antigens is unaffected but that too in thymus- dependent antigens may be inhibited.
• ALS being a foreign protein, may lead to hypersensitivity reaction.
• It mainly acts on circulating lymphocytes and not on lymphocytes in lymphoid organs.
• It is mainly used in the prevention of graft rejections.
• Monoclonal antibodies against specific lymphocyte membrane antigens are now available.

References: 

i) https://academic.oup.com/bmb/article-abstract/19/3/207/257681?redirectedFrom=PDF

ii) https://www.news-medical.net/health/What-Factors-Affect-Antibody-Production.aspx

Factors affecting antibody production