Acquired immune response

1. Acquired Immune Response

The acquired immune response, also known as the adaptive immune response, is a critical component of the immune system that provides a targeted and specific defense against pathogens. Unlike the innate immune response, which is immediate and non-specific, the acquired immune response is highly specific to the particular pathogen that has invaded the body. This specificity is achieved through the recognition of antigens, which are unique molecules found on the surface of pathogens.

Components of the Acquired Immune Response

The acquired immune response involves several key components:

Lymphocytes

The primary cells involved in the acquired immune response are lymphocytes, which are a type of white blood cell. There are two main types of lymphocytes:

• B cells: These cells are responsible for producing antibodies, which are proteins that specifically bind to antigens. This binding can neutralize the pathogen or mark it for destruction by other immune cells.

• T cells: These cells do not produce antibodies but instead directly attack infected cells or help coordinate the immune response. T cells can be further divided into:

 * Helper T cells: These cells assist other cells in the immune response by releasing signaling molecules called cytokines.
 * Cytotoxic T cells: These cells directly kill infected cells by recognizing antigens presented on the surface of these cells.

Antigen Presentation

For the acquired immune response to be activated, antigens must be presented to lymphocytes. This is done by antigen-presenting cells (APCs) such as dendritic cells, macrophages, and B cells. These cells process the pathogen and present its antigens on their surface using major histocompatibility complex (MHC) molecules.

Memory Cells

One of the hallmarks of the acquired immune response is the formation of memory cells. After an initial exposure to a pathogen, some B and T cells become memory cells, which persist in the body and provide a faster and more robust response upon subsequent exposures to the same pathogen. This is the basis for immunological memory and is the principle behind vaccination.

Phases of the Acquired Immune Response

The acquired immune response can be divided into several phases:

1. Recognition: Lymphocytes recognize specific antigens presented by APCs. 2. Activation: Upon recognition, lymphocytes become activated and proliferate. 3. Effector Phase: Activated lymphocytes carry out their functions, such as producing antibodies or killing infected cells. 4. Resolution: Once the pathogen is cleared, most effector cells die off, but memory cells remain.

Also see

• Innate immune response
• Antigen
• Antibody
• Vaccination
• Immunological memory