How immune memory is lead to efficacy of vaccines

Question

How the immune memory is lead to the efficacy of vaccines and also produces allergies?

Answer 1

Vaccines are controlled inoculations of the fragments of infectious agents or of inactive infectious agents to encourage the primary immune response, the making of particular memory B lymphocytes alongside the antigen. Thus the organism generates immunoglobulins and becomes ready to destroy antigens whenever exposed to new infections by such agents. In allergies the humoral immune system is sensitized (that is, makes antibodies and particular memory B lymphocytes) against some general environmental substances wrongly familiar as antigens. For illustration, dust particles, pollen-derived substances, compounds existed in foods or in medicines and so on might be identified as antigens triggering the main response and creating an immune memory against them which then become causes of allergy. The more the individual is exposed to such substances the more severe is the immune reaction.

The IgE antibodies which cause allergy bind to receptors of leukocytes termed as mastocytes whose cytoplasm is packed of histamine granules. The antibody-mastocyte bond causes such cells to discharge a great quantity of histamine in the circulation, stimulating inflammation and producing the allergic symptoms and signs. For this cause allergy is treated with antihistamines, drugs which block the histaminic reaction. The Exacerbated allergic reactions, for illustration, in hypersensitivity to some medicines such as penicillin and sulfas, might cause anaphylactic shock, a rigorous clinical condition which sometimes leads to death.