CD4+CD28- costimulation-independent T cells in multiple sclerosis

Area of Science:

• Immunology
• Neuroscience
• Autoimmunity

Background:

• Multiple sclerosis (MS) pathogenesis involves autoimmune responses against myelin antigens mediated by CD4+ lymphocytes.
• Activated myelin-specific cells are frequently observed in MS patients, highlighting their central role in disease development.

Purpose of the Study:

• To identify and characterize a unique CD4+ T-cell subpopulation involved in initiating autoimmune responses in MS.
• To investigate the functional properties and potential pathogenic role of CD4+CD28- T-cells in the central nervous system (CNS).

Main Methods:

• Phenotypic characterization of CD4+ T-cells, focusing on CD28 and CTLA-4 expression.
• Functional assays assessing T-cell activation, cytokine secretion (IFN-gamma), and growth characteristics independent of costimulation.
• Analysis of CD4+CD28- T-cell populations in a subgroup of MS patients.

Main Results:

• A CD4+ T-cell subpopulation lacking CD28 (CD4+CD28-) was identified, exhibiting CD28-independent activation and Th1 cytokine secretion.
• These CD4+CD28- cells demonstrated enhanced IFN-gamma production, upregulated IFN-gamma and IL-12Rbeta2 expression without costimulation, and increased survival due to lack of CTLA-4.
• The CD4+CD28- population was expanded in a subset of MS patients, with myelin basic protein-specific cells found within this subset.

Conclusions:

• CD4+CD28- T-cells possess the potential to initiate autoimmune responses in the CNS due to their costimulation-independent activation.
• These cells may contribute significantly to the inflammatory process in the CNS of MS patients, particularly those with expanded CD4+CD28- populations.