BSC 310 Lecture Notes - Lecture 38: Elisa, Immunofluorescence, Complement Fixation Test
Cell Mediated Immunity (CMI)‐
Cell mediated immunity depends upon the activity of T lymphocytes. T lymphocytes ‐ ‐ ‐
have a longer life span than B lymphocytes and are found in the same lymphatic tissues‐
as the B lymphocytes. The T lymphocytes react with certain antigenic determinants and‐ ‐
become immunologically “committed.” Part of this commitment is the conversion to a
subset of cells called cytotoxic T lymphocytes.‐
Activity of cytotoxic T-lymphocytes. Cytotoxic T-lymphocytes do not produce antibody
molecules. Rather, they leave the lymphatic tissues and enter the circulation. They circulate
through the blood vessels and gather at the infection site. Here they interact directly with
organisms such as fungi, protozoa, cancer cells, and transplant cells. They also interact with
virus-infected cells and bacteria-infected cells (such as lung cells infected with tuberculosis).
The T-lymphocytes exert a “lethal hit” on the cells and secrete substances into them that
lead to cellular destruction.
In addition to their direct interaction, T-lymphocytes also secrete substances
calledlymphokines. Lymphokines attract phagocytes to the area and encourage them to
perform phagocytosis on fungi, protozoa, and infected cells. This activity helps relieve the
infection. Lymphokines are also known as cytokines. An important cytokine isinterleukin-1,
which activates T-lymphocytes, causing them to proliferate further and form clones.
Helper and suppressor T-lymphocytes. Helper T-lymphocytes also function in the immune
system by encouraging the activity of B-lymphocytes in the production of
antibodies. Suppressor T-lymphocytes regulate or suppress the activity of the immune
system so that it is not excessive. Natural killer (NK) cells are T-lymphocytes that recognize
and destroy many types of target cells without being exposed to antigens. Technically,
these are not part of the specific immune response. Finally, the delayed hypersensitivity T-
lymphocytes function in hypersensitivity reactions and encourage local tissue inflammations.
Detecting Antibodies with Laboratory Tests
Certain laboratory tests are available to detect the presence of antibodies in an
individual. These laboratory tests are commonly used in diagnostic procedures because
the presence of a certain antibody indicates the presence of a certain disease. The
study of serum for its antibody content is known as serology.
One of the objects of serology is to determine the titer of antibody present in the individual.
The titer is an estimate of the antibody level in a unit volume of serum. It is determined as a
reactive dilution of the serum and is usually expressed in a ratio such as 1:100.
The agglutination and precipitation tests. Serological tests that involve clumping of an antigen
are called agglutination tests. Antibodies involved in agglutination tests are
called agglutinins. When the antibody molecules unite with antigen molecules on the surface
of bacteria, red blood cells, or particles, they cause the cells to stick together and form large
clumps (Figure 1 ).
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Document Summary
Cell mediated immunity depends upon the activity of t lymphocytes. T lymphocytes have a longer life span than b lymphocytes and are found in the same lymphatic tissues as the b lymphocytes. The t lymphocytes react with certain antigenic determinants and become immunologically committed. part of this commitment is the conversion to a subset of cells called cytotoxic t lymphocytes. Rather, they leave the lymphatic tissues and enter the circulation. They circulate through the blood vessels and gather at the infection site. Here they interact directly with organisms such as fungi, protozoa, cancer cells, and transplant cells. They also interact with virus-infected cells and bacteria-infected cells (such as lung cells infected with tuberculosis). The t-lymphocytes exert a lethal hit on the cells and secrete substances into them that lead to cellular destruction. In addition to their direct interaction, t-lymphocytes also secrete substances calledlymphokines.
