The specific or adaptive immunity, also known as acquired immunity, is the set of responses activated by the immune system to target specific pathogens. It can be acquired in a natural and active form (when the immune system retains the memory of previous diseases, such as naturally acquired active immunity), a naturally passive form (due to preformed antibodies from the mother, that also transfer the acquired natural immunity or passive immunity to the new born), and/or artificially (by the administration of vaccines and serums, also called artificially acquired immunity).

In general, the active forms of immunity are long lived, particularly in cases of clinical infections. On the other hand, passive forms of immunity are short lived because the antibodies eventually die or are removed from the body as foreign proteins. Artificial immunity or vaccinations may cause an immunity that is long lived, but studies have shown that vaccinations may not last as long as hoped.


What is specific or adaptive immunity?

While the nonspecific immunity is the oldest defence system that is found in all multicellular organisms, including insects and plants, specific immunity or acquired immunity appears in the vertebrates.

There are two types of white blood cells known as lymphocytes that are essential to the specific immune response. The white blood cells are produced in the bone marrow and later develop into one of several subcategories. The most common lymphocytes are the T cells and B cells.

In the presence of a pathogen the specific immunity is based on targeted activation of B and T lymphocytes, specialized cells in the immune function, and it is characterized by the important specificity of the receptors involved (antibodies in the case of B-lymphocytes and T-cell receptor, which is the T cell receptor, in the case of T lymphocytes).

The strategies through which it performs its functions are two specific immunities that cooperate closely with each other: the humoral immunity (via the blood) and cell-mediated immunity. In humoral immunity, the first to intervene are the B cells, which are activated to produce antibodies to eradicate the infectious agents. In cell-mediated immunity the T cells are activated to secrete some inflammatory molecules, cytokines, and revealing their cytotoxic properties. The memory – or the ability to respond faster and more effective against previously recognized infectious agents – is a key feature of specific immunity.

Furthermore, the cells that make up the specific immunity circulate in the blood, but they can also be found in different organs in the body. The immune tissues in the organs facilitate the cells’ maturation, capture the pathogens and provide a place where the immune cells can produce a specific immune response. Some of the organs and tissues involved in the specific immunity include the bone marrow, spleen, thymus gland, lymph nodes, and the tonsils.


What function does the specific or adaptive immunity serve?

The specific immunity is the system through which an organism defends itself in the presence of agents that are foreign by specifically targeting those agents. The mechanisms of specific immunity often overlap with the typical non-specific immunity in order to enhance the immune response.