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Each antibody recognizes a specific antigen unique to its target. By binding their specific antigens, antibodies can cause agglutination and precipitation of antibody-antigen products, prime for phagocytosis by macrophages and other cells, block viral receptors, and stimulate other immune responses, such as the complement pathway.
Once exposed to an antigen, the naive B cell either becomes a memory B cell or a plasma cell that secretes antibodies specific to the antigen that was originally bound. Plasma cells do not last long in the circulation; this is in contrast to memory cells that last for very long periods of time.
In contrast, the naive plasma cell is fully differentiated and cannot be further stimulated by antigen to divide or increase antibody production. Memory B cell activity in secondary lymphatic organs is highest during the first 2 weeks after infection. Subsequently, after 2 to 4 weeks its response declines.
Cellular immunity, also known as cell-mediated immunity, is an immune response that does not rely on the production of antibodies. Rather, cell-mediated immunity is the activation of phagocytes, antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen.
However, without knowing the correlates of immunity, scientists cannot know exactly what sort of immune response a vaccine would need to stimulate, and the only method of assessing vaccine effectiveness will be through large phase III trials with clinical outcomes (i.e. infection and/or disease, not just laboratory markers). [citation needed]
The immune system may respond in multiple ways to an antigen; a key feature of this response is the production of antibodies by B cells (or B lymphocytes) involving an arm of the immune system known as humoral immunity. The antibodies are soluble and do not require direct cell-to-cell contact between the pathogen and the B-cell to function.
A representation of the cholera epidemic of the 19th century. For thousands of years mankind has been intrigued with the causes of disease and the concept of immunity. The prehistoric view was that disease was caused by supernatural forces, and that illness was a form of theurgic punishment for "bad deeds" or "evil thoughts" visited upon the soul by the gods or by one's enemies. [8]
In immunology, passive immunity is the transfer of active humoral immunity of ready-made antibodies.Passive immunity can occur naturally, when maternal antibodies are transferred to the fetus through the placenta, and it can also be induced artificially, when high levels of antibodies specific to a pathogen or toxin (obtained from humans, horses, or other animals) are transferred to non-immune ...