Phenotype and morphology of murine NC-1.1+ natural cytotoxic cells

The morphology and phenotype of cells identified by the anti-NC-1.1 mAb, 1C4, were studied in CBA and (CBA x C57BL/6) F1 mice. This mAb blocked splenic natural cytotoxic (NC) cell activity in vitro and in vivo. Single colour flow cytometric analysis showed that 6 +/- 1% of all CBA splenocytes were NC-1.1+, and that granular cells of varying sizes, as defined by their forward and side light scatter, contained the highest proportion of NC-1.1+ cells (29 +/- 7%). When analysed by two colour flow cytometry, the large and the granular NC-1.1+ spleen cells in CBA mice were shown to co-express Thy-1.2 and L3T4 (< or = 33%), Mac-1 (< or = 26%), IgM (< or = 60%) and FcR gamma II and J11d (< or = 100%). In contrast, T cell markers were not co-expressed on the small agranular NC-1.1+ spleen cells. This pattern of marker expression was evident in CBA spleens from 2 days of age. When (CBA x C57BL/6) F1 spleen cells were similarly analysed, 82% of granular NC-1.1+ cells also co-expressed NK-1.1. Single colour analysis of CBA bone marrow, thymus, lymph node and peripheral blood leucocytes revealed that < or = 10% of all cells examined were NC-1.1+ while the most granular cells in these organs were 16-43% NC-1.1+. These results support the 'horizontal lineage' theory that NC cells are cells of different lymphohaemopoietic cell lineages at particular stages of differentiation.