Increased protein kinase C activity in human memory T cells

Area of Science:

• Immunology
• Cell Biology

Background:

• Differentiated T cells, including memory T cells, express surface antigens like CD26.
• CD26+ T cells exhibit enhanced responses to activation stimuli and increased T cell receptor (TCR)/CD3 complex phosphorylation.
• This suggests a role for protein kinase C (pkC) in the heightened responsiveness of memory T cells.

Purpose of the Study:

• To investigate the biochemical basis of immune memory by focusing on the CD26+ T cell population.
• To determine the distribution and activity of pkC in CD26+ versus CD26- T cells.
• To elucidate the relationship between CD26 expression, pkC activity, and T cell activation.

Main Methods:

• Peripheral blood T cells were sorted into CD26+ and CD26- populations.
• pkC activity was measured in cytosolic fractions of sorted T cells.
• Proliferative responses to TCR/CD3, CD2, and phorbol ester (PMA) stimulation were assessed.
• The effect of a pkC inhibitor (staurosporine) and PMA on T cell proliferation and CD26 expression was evaluated.

Main Results:

• The majority of pkC activity was found in the cytosol of memory (CD26+) T cells.
• CD26+ T cells displayed increased proliferation upon activation, which was inhibited by staurosporine.
• PMA treatment, known to deplete pkC activity, down-regulated CD26 expression on CD26+ T cells and inhibited PHA-induced CD26 expression on CD26- T cells.

Conclusions:

• Enhanced pkC activity is directly demonstrated in memory (CD26+) T cells.
• Increased pkC activity is associated with the characteristic enhanced proliferative response of memory T cells.
• A functional relationship exists between CD26 expression and pkC activity in T cells, contributing to memory function.