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The classical and alternate pathways of T cell activation are impaired in leprosy
V Muthukkaruppan1, H R Chakkalath, S Malarkannan
1Department of Immunology, School of Biological Sciences, Madurai Kamaraj University, India.
Abstract:
The proliferative response of circulating T lymphocytes from bacterial index-positive lepromatous patients to mitogenic anti-CD3 and pairs of anti-CD2 monoclonal antibodies was significantly reduced. In these patients, the CD2 but not CD3 receptor expression was down-regulated. Further, the CD2 modulation and the associated suppression of proliferative response to monoclonals was brought about in T cells of healthy subjects by prior incubation of mononuclear cells in vitro with Mycobacterium leprae. Thus, the T cell activation pathways through the CD3 and CD2 receptors are impaired in lepromatous leprosy patients and the impairment appears to be due to the modulation of the CD2 receptor specifically by M. leprae.
Insights
T cell responses are impaired in leprosy patients due to Mycobacterium leprae. This bacterium down-regulates CD2 receptor expression, hindering T cell activation and proliferation.
Area of Science:
- Immunology
- Microbiology
- Cell Biology
Background:
- Leprosy, caused by Mycobacterium leprae, is a chronic infectious disease primarily affecting the skin and peripheral nerves.
- T lymphocytes play a crucial role in cell-mediated immunity against intracellular pathogens like M. leprae.
- Impairment of T cell function is a hallmark of lepromatous leprosy, the more severe form of the disease.
Purpose of the Study:
- To investigate the functional status of T lymphocytes in lepromatous leprosy patients.
- To determine the role of CD3 and CD2 receptors in T cell activation in the context of M. leprae infection.
- To elucidate the mechanism by which M. leprae might impair T cell responses.
Main Methods:
- Assessing the proliferative response of T lymphocytes from lepromatous leprosy patients to anti-CD3 and anti-CD2 monoclonal antibodies.
- Quantifying the expression levels of CD3 and CD2 receptors on T cells.
- In vitro incubation of healthy donor mononuclear cells with Mycobacterium leprae to mimic disease conditions.
Main Results:
- Circulating T lymphocytes from lepromatous leprosy patients showed a significantly reduced proliferative response to mitogenic anti-CD3 and anti-CD2 antibodies.
- CD2 receptor expression was down-regulated on T cells from these patients, while CD3 expression remained unaffected.
- In vitro exposure of T cells from healthy individuals to M. leprae resulted in CD2 modulation and suppressed proliferative responses.
Conclusions:
- T cell activation pathways involving CD3 and CD2 receptors are impaired in lepromatous leprosy.
- The impairment appears to be specifically caused by Mycobacterium leprae modulating the CD2 receptor.
- This modulation of CD2 by M. leprae contributes to the suppressed T cell immunity observed in lepromatous leprosy.