Basic Immunology (6th Edition) Edit edition

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The adaptive immunity also known as acquired immunity consists of highly specialized systems and cells which work in a stepwise cascade of reactions to eliminate the pathogens or prevent their growth.

The two types of adaptive immunity are as under

1. Humoral immunity: It is also called as antibody-mediated immunity. In this type of immunity antibodies are produced by plasma B-cells against specific antigen. Plasma B-cells are differentiated from B-cells with the help of helper T-cells. These antibodies then kill the target.

2. Cell-mediated immunity: This type of immunity is mediated by T-lymphocytes and hence the name. This immunity occurs inside infected cells. In this type of immunity, the antigen of a pathogen is expressed on APCs (antigen presenting cells). Cytokines secreted by helper T-cells help the T-lymphocytes to bind to the infected cells through MHC (major histocompatibility complex) molecules leading to the differentiation of T-lymphocytes into cytotoxic T-cells. The infected cell ultimately dies of lysis.

Humoral immunity combats pathogens that are circulating freely or occur outside the infected cells like certain viruses and bacteria.

Cell-mediated immunity destroys intracellular pathogens and infected host cells in order to prevent further expansion of the disease.