Expression and role of phosphatidylcholine-specific phospholipase C in human NK and T lymphocyte subsets.
We recently reported evidence of phosphatidylcholine-specific phospholipase C (PC-PLC) involvement in NK cell-mediated cytotoxicity and in lytic granule exocytosis. In the present study, different subpopulations of human PBL were investigated in relation to PC-PLC enzyme expression. While a substantial intracellular amount of PC-PLC was detected in all lymphoid subsets, expression of this enzyme on the outer membrane surface reached high levels only in NK cells, was present at low levels in B lymphocytes and in some TCR gamma/delta T cells and was practically absent in CD4(+) and CD8(+ )T lymphocytes. Moreover, in NK cells two different subpopulations were identified, CD56(dim) PC-PLC(bright) and CD56(bright) PC-PLC(low/-) cells, corresponding to distinct subsets with cytolytic and immunoregulatory functions, respectively. Interestingly, the PC-PLC expression level on the NK membrane surface correlated closely with that of the CD16 receptor, suggesting a possible relationship between enzyme externalization and NK cell maturation. In summary, our results suggest that a high PC-PLC expression on the cell membrane surface of PBL is a peculiarity of NK cytolytic cells, in which the enzyme is apparently involved in the ability of this subset to lyse sensitive target cells.
Spadaro
Francesca
F
Department of Cell Biology and Neurosciences, Istituto Superiore di Sanità, Rome, Italy.
Cecchetti
Serena
S
Sanchez
Massimo
M
Ausiello
Clara Maria
CM
Podo
Franca
F
Ramoni
Carlo
C
D000328:Adult; D002478:Cells, Cultured; D003601:Cytotoxicity Tests, Immunologic; D003602:Cytotoxicity, Immunologic; D006801:Humans; D007694:Killer Cells, Natural / Q000201:enzymology* / Q000276:immunology*; D013379:Substrate Specificity; D016176:T-Lymphocyte Subsets / Q000201:enzymology* / Q000276:immunology*; D010738:Type C Phospholipases / Q000096:biosynthesis* / Q000502:physiology
D010738:Type C Phospholipases; C105598:phosphatidylcholine-specific phospholipase C