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Inverse relationship of CA2+ mobilization and cell proliferation in CD8+ memory and virgin T cells
T Schlunck1, W Schraut, G Riethmüller
1Institute for Immunology, University of Munich, FRG.
Insights
Memory CD8 T cells show increased calcium (Ca2+) influx but reduced proliferation after phytohemagglutinin stimulation, unlike virgin T cells. This suggests an inverse relationship between Ca2+ mobilization and proliferation in CD8 T cell subsets.
Area of Science:
- Immunology
- Cellular Biology
- T cell immunology
Background:
- Memory T cells are crucial for adaptive immunity but their functional properties compared to virgin T cells are not fully understood.
- Monoclonal antibodies can define T cell subsets, yet functional differences require detailed investigation.
Purpose of the Study:
- To compare the functional properties, specifically calcium (Ca2+) mobilization and proliferation, of memory and virgin T cells within CD4 and CD8 subsets.
- To investigate the role of phytohemagglutinin (PHA) in stimulating these T cell responses.
Main Methods:
- Utilized two-color fluorescence for cell surface staining and Ca2+ indicator indo-1.
- Analyzed Ca2+ influx and cell proliferation in CD4 and CD8 T cell subsets.
- Defined memory and virgin T cells using monoclonal antibodies UCHL1 and Leu-18.
Main Results:
- CD8+UCHL1+ memory T cells exhibited a 1.5-fold higher Ca2+ influx compared to CD8+UCHL1- virgin T cells, a finding consistent with reciprocal markers.
- CD8+UCHL1- virgin T cells showed strong proliferation in response to PHA, whereas CD8+UCHL1+ memory T cells displayed minimal to absent proliferation (6-fold lower cpm).
- No clear Ca2+ influx pattern was observed in CD4 subsets; functional differences were primarily noted in the CD8 compartment.
Conclusions:
- Ca2+ mobilization and proliferation are inversely correlated in CD8 T cells following PHA stimulation.
- CD8 memory T cells demonstrate high Ca2+ mobilization but low proliferation, while naive CD8 T cells show the opposite response.
- These findings suggest that vigorous initial responses of memory T cells might be regulated by negative control mechanisms.
Abstract:
Memory T cells can now be defined with various monoclonal antibodies but little is known about the functional properties of these cells as compared to virgin T cells. We have studied Ca2+ mobilization and proliferation of memory and virgin cells in both the CD4 and CD8 subsets in response to phytohemagglutin-in. Using two-color fluorescence (yellow, red) for cell surface staining combined with two-color fluorescence for the Ca2+ chelator indo-1 (violet, blue) we can demonstrate that CD8+UCHL1+ memory cells exhibit a 1,5-fold higher influx than the CD8+UCHL1- virgin cells. The same pattern was obtained when CD8 memory and virgin cells were defined by a reciprocal marker (Leu-18) indicating that the higher response of memory CD8 cells is independent of the monoclonal antibody used to identify the cells. For the respective CD4 subsets no such clear-cut pattern of Ca2+ influx was evident. Analysis of proliferation in both subsets indicates that CD8+UCHL1- cells strongly proliferate in response to PHA, while CD8+UCHL1+ memory cells show only a minimal response with the average cpm values being 6-fold lower. In some instances no proliferation at all was detectable in the CD8+UCHL1+ cells. Identification of the subsets by reciprocal markers confirmed the lower proliferative response in the CD8 memory cells. Hence, within the CD8 compartment the memory cells, after phytohemagglutinin stimulation, exhibit a high Ca2+ mobilization but a low to absent proliferation, while the converse is true for the naive cells. These data show that (a) Ca2+ mobilization and proliferation are inversely correlated and (b) an initially vigorous response of memory cells may be subject to negative control mechanisms.