CD53 induces CD2-independent homotypic clustering of NK cells.

<p>A) Purity of 12 day-old LAK cells, as determined by staining with anti-CD3 and anti-NKR-P1A. LAK cells were cultured for 2 h in the presence of soluble antibodies towards CD53, CD2, NKR-P1A, or an isotype control IgG. B) Cluster formation was photographed with a light microscope, or C) quantified by counting the number of free, non-aggregated cells in treated samples relative to cells cultured in medium using a hemocytometer. D and E) LAK cells were co-cultured for up to 2 h with antibodies towards CD53 and CD2 or with CD53 and isotype control antibody. Cluster formation was assessed qualitatively by microscopy (D), or quantitatively by hemocytometer (E) as described above. Results are presented as the mean±SEM of 3 independent experiments with samples in duplicates (n = 6). Comparisons within an experimental group were performed with the One-way analysis of variance (ANOVA) and a <i>post hoc</i> Tukey's multiple comparisons test to compare treated samples to untreated sample. *, p<0.05; **, p<0.005; ***, p<0.001.