Cellular and Humoral Immunity Notes PDF

Humoral immunity and Cellular immunity are two kinds of adaptive immunity during which a particular immunologic response is produced for a specific pathogen. In humoral immunity, antibodies are produced by the plasma T-cells. While in the case of cell-mediated immunity, T cells induce the apoptosis of the infected cells. Humoral immunity destroys the extracellular pathogens while cell-mediated immunity destroys the intracellular pathogens.

Humoral Immunity

Humoral immunity is the immunity that works by circulating antibodies. Humoral immunity is a component of adaptive immunity, which generates specific immune responses to a specific foreign material. The extracellular spaces of the body are protected with the help of humoral immunity. Most pathogens that invade the body multiply within the extracellular spaces. Intracellular pathogens move from one cell to a different one through the extracellular space. Therefore, extracellular space is a vital place to destroy pathogens. Plasma B cells are responsible for the production and secretion of antibodies.

Generally, the activation of B cells occurs in T helper cells. Antibodies destroy pathogens in 3 ways. They bind to the precise molecules on the surface of the pathogen, neutralizing the pathogen. This neutralized pathogen is unable to enter into the cells. It’s also important to stop bacterial toxins. The antibody-linked pathogens are subjected to phagocytosis by macrophages and other cells. This process is known as opsonization. The complement system gets activated once antibodies bind to the pathogens. The complement proteins bind to the antibody-linked pathogens and recruit phagocytic cells.

Cellular Immunity

Cell-mediated immunity or Cellular immunity is the immunity mediated by antigen-specific T cells. T cells are produced within the bone marrow and are matured within the thymus. After they enter the bloodstream, T cells are often found within the blood and lymphatic tissue. The antigens should be presented on the antigen-presenting cells (APCs) surface alongside the main histocompatibility complexes (MHC). Once T cells face an antigen, they proliferate and differentiate into armed effector cells.

The cytotoxic T cells destroy the infected cells by inducing apoptosis. T helper cells stimulate plasma B cells to supply antibodies. The IgG and IgM are the most two sorts of antibodies produced by T helper cells in response to plasma B cells. The memory T cells are differentiated, but their action requires the activation by the precise antigen. The main characteristic feature of cell-mediated immunity is that it destroys intracellular pathogens.

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