Immune response: Humoral and Cell mediated immunity.

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The immune response involves two primary branches: humoral immunity and cell-mediated immunity. These two branches work together to protect the body from various pathogens, including bacteria, viruses, and other foreign substances.

  1. Humoral Immunity:

    • Humoral immunity, also known as antibody-mediated immunity, is primarily mediated by B lymphocytes (B cells) and the antibodies they produce.
    • B cells are specialized white blood cells that have surface receptors capable of recognizing specific antigens (molecules on the surface of pathogens).
    • When a B cell encounters an antigen that matches its receptor, it undergoes activation and differentiation into plasma cells.
    • Plasma cells are antibody factories; they produce large quantities of antibodies, also known as immunoglobulins, that are specific to the antigen.
    • Antibodies are proteins that circulate in the blood and other body fluids. They can neutralize pathogens directly by binding to them and preventing them from infecting cells or by marking them for destruction by other immune cells.
    • Humoral immunity is highly effective against extracellular pathogens, such as bacteria and toxins, that are present in the bloodstream or body fluids.
    • Memory B cells are also generated during the immune response, providing long-lasting immunity by "remembering" previous infections or vaccinations.

  2. Cell-Mediated Immunity:

    • Cell-mediated immunity is primarily mediated by T lymphocytes (T cells).
    • T cells do not produce antibodies but instead recognize antigens presented on the surface of infected cells or other antigen-presenting cells.
    • There are two main types of T cells involved in cell-mediated immunity: cytotoxic T cells (CD8+ T cells) and helper T cells (CD4+ T cells).
    • Cytotoxic T cells can directly kill infected cells by releasing toxic substances, such as perforin and granzymes, or by inducing apoptosis (programmed cell death) in the infected cell.
    • Helper T cells play a crucial role in regulating the immune response. They help activate other immune cells, including B cells, cytotoxic T cells, and macrophages, by releasing signaling molecules called cytokines.
    • Cell-mediated immunity is essential for combating intracellular pathogens, such as viruses, some bacteria, and parasites, which live inside host cells and are not easily targeted by antibodies.
    • Memory T cells are also generated during the immune response, providing long-term immunity against previously encountered pathogens.

In summary, humoral immunity involves the production of antibodies by B cells to neutralize extracellular pathogens, while cell-mediated immunity involves the activation of T cells to target and destroy infected cells. These two branches of the immune system complement each other and work together to provide a comprehensive defense against a wide range of pathogens.

 

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