Relationship between target cell recognition and temporal fluctuations in intracellular Ca2+ of human NK cells.
Temporal changes in intracellular Ca2+ concentration, [Ca2+]i, of resting human peripheral blood NK cells in response to target cell binding were evaluated by flow cytometry. [Ca2+]i was significantly elevated in PBL and purified NK cells bound to NK-sensitive K562 and HSB2 target cells, but not in those bound to NK-resistant MD1 B-lymphoblastoid cells. Thus, a) the ability of a target cell to elicit a Ca2+ flux response correlated with its sensitivity to lysis of NK cells, and b) adhesion alone was not a sufficient stimulus for response induction. Conjugates of NK cells bound to K562 target cells were sorted onto agarose-coated slides on the basis of relative NK cell [Ca2+]i and evaluated in 19-hr single cell agarose cytotoxicity assays. In contrast to those with basal levels of [Ca2+]i, NK cells with elevated [Ca2+]i bound more strongly to target cells, as judged by the stability of conjugates to sort-related shear forces (p less than 0.01), and more frequently killed the target cell to which they were attached (p less than 0.05). Temporal fluctuations in [Ca2+]i were observed in target-bound NK cells in both the presence and absence of extracellular Ca2+. Thus, influx of extracellular Ca2+ and release of Ca2+ from internal stores both appeared to contribute to the NK cell Ca2+ flux response triggered by adhesion to appropriate target cells. These results support the hypothesis that such fluctuations in NK cell [Ca2+]i constitute an early signal flagging the occurrence of NK cell recognition.
Edwards
B S
BS
Biomedical Research Division, Lovelace Medical Foundation, Albuquerque, NM 87108.
Nolla
H A
HA
Hoffman
R R
RR
D002118:Calcium / Q000378:metabolism* / Q000502:physiology; D015220:Calcium Channels / Q000378:metabolism / Q000502:physiology; D002448:Cell Adhesion; D003593:Cytoplasm / Q000378:metabolism / Q000502:physiology; D003601:Cytotoxicity Tests, Immunologic; D003602:Cytotoxicity, Immunologic; D005110:Extracellular Space / Q000378:metabolism / Q000502:physiology; D006801:Humans; D007694:Killer Cells, Natural / Q000276:immunology* / Q000378:metabolism / Q000502:physiology; D015290:Second Messenger Systems; D013997:Time Factors
D015220:Calcium Channels; D002118:Calcium