ANATOMY

Detailed explanation-1: -Active immunity is long-lasting, and sometimes life-long.

Detailed explanation-2: -B lymphocytes are the cells of the immune system that make antibodies to invading pathogens like viruses. They form memory cells that remember the same pathogen for faster antibody production in future infections.

Detailed explanation-3: -Most lymphocytes are short-lived, with an average life span of a week to a few months, but a few live for years, providing a pool of long-lived T and B cells. These cells account for immunologic “memory, ” a more rapid, vigorous response to a second encounter with the same antigen.

Detailed explanation-4: -The ability to change the isotype of antibody produced (class switching) by a B cell also occurs in germinal centres and requires AID. In a secondary response to the same antigen, memory cells are rapidly activated. This process is quicker and more effective than the primary response.