Fig. 4

Clustering of PD1^hi cells. a Left hand panels are density plots representing PD1^hi (top) and FOXP3 (bottom) for one case (lymph node tissue). The impression of greater clustering of PD1^hi cells is confirmed by statistical analysis using Ripleys K function (right hand panels). A measure of distance (r) on the x-axis is plotted against K(r) function on the y-axis. The curve for complete spatial randomness (CSR) (dotted red line) is compared to K function for MZL (solid black line) for PD1 (upper panel) and FOXP3 (lower panel). Greater upward deflection of the observed curve compared to CSR represents greater clustering with the difference between these curves calculated to provide an overall cluster score. b Cluster scores for MZL cases (n = 15). PD1^hi cells are significantly more clustered than FOXP3⁺ cells (Mann-Whitney test, P < 0.01). c Immunofluorescence images. CD20 (green), Ki-67 (blue) and PD1 (red) staining of a lymph node from a patient with MZL. Low power (10×) views of the merged antibody stains show that proliferating cells occur in clusters. Three fields are shown as high power views (80×). Two of these fields are from regions that contain a high density of Ki-67⁺ cells (upper and lower rows) while the middle row is from a region of lower Ki-67⁺ density