Adaptive secondary immunity

Adaptive (Specific) Secondary Immunity - An Overview

Definition: Adaptive secondary immunity, also known as acquired immunity, refers to immunity that an organism develops after exposure to a specific pathogen. This type of immunity is ‘adaptive’ because it improves upon subsequent encounters with the same pathogen.
Types: There are two types of adaptive secondary immunity - active immunity and passive immunity. Active immunity is initiated by the body’s immune system in response to exposure to a pathogen, whereas passive immunity is borrowed from another source and it lasts for a short period of time.

Components of Adaptive Secondary Immunity

Lymphocytes: Lymphocytes are a type of white blood cell that plays a central role in adaptive immunity. There are two major types of lymphocytes - B cells and T cells. B cells produce antibodies that bind to pathogens and neutralise them, while T cells directly attack infected cells.
Antibodies: Antibodies, or immunoglobulins, are proteins produced by B cells. They recognise and bind to specific antigens on the pathogen’s surface, marking them for destruction.
Memory cells: After an infection, some of the B and T cells transform into memory cells. These cells are responsible for the quick response in case of a subsequent infection with the same pathogen.

Active and Passive Immunity

Active immunity: This form of immunity occurs when the body’s immune system responds to an infection or vaccination by producing antibodies and memory cells. This process takes several days, but the immunity is long-lasting, often providing protection for many years, or even a lifetime.
Passive immunity: This involves the transfer of antibodies from one individual to another. An example is the antibodies a baby receives from its mother during breastfeeding. This immunity is temporary as the transferred antibodies gradually decrease.

T Cell Responses

Helper T cells: These cells recognise the antigen presented by the infected cells and produce cytokines to stimulate B cells to produce antibodies and cytotoxic T cells to destroy infected cells.
Cytotoxic T cells: These cells recognise and kill infected cells directly. They also produce memory T cells for long-term protection.

B Cell Responses

Plasma B cells: Once activated, B cells differentiate into plasma cells. These are the cells that produce antibodies specific to the detected antigen.
Memory B cells: Similar to T cells, B cells also produce memory cells to provide long-term protection against future infections by the same pathogen.

Remember, successful adaptive immune responses often require the interactions of multiple cellular components to eliminate pathogens and generate an effective memory response against future infections.