What immune elements are involved in a positive skin test for tuberculosis?

A positive skin test for tuberculosis, commonly known as the Mantoux test, indicates a delayed-type hypersensitivity reaction primarily mediated by T cells and macrophages. This test assesses the immune system's response to the tuberculin purified protein derivative (PPD), which is a protein derived from the tuberculosis bacteria.

When a person is exposed to the tuberculosis bacterium, specific T cells, particularly CD4+ T helper cells, are activated. These T cells release cytokines that recruit and activate additional immune cells, such as macrophages, which play a crucial role in the immune response against the tuberculosis pathogen. The interaction between T cells and macrophages results in a local inflammatory response leading to the characteristic induration (swelling) observed at the skin test site.

Other types of immune components, such as IgE antibodies, are primarily involved in immediate hypersensitivity reactions and do not play a significant role in the delayed response tested in the skin test. Similarly, the involvement of NK cells and IgG antibodies, or B cells and IgM antibodies, does not apply to this particular hypersensitivity reaction, as they are not responsible for the immune response assessed in the skin test for tuberculosis.