CD100-bound PTP activity is not due to association of CD100 with CD45 PTP in XG-1 cells.

Cell lysates were CD45-immunodepleted before CD100 or CD45 immunoprecipitations and PTP assays, as described in Figure 2 and detailed in “Materials and Methods.” Immunodepletions of CD101 (not expressed on XG-1 cells) with the BB27 mAb were used as negative control depletions. Basal levels of PTP activity were measured in immunoprecipitates from undepleted lysates. CD101 immunoprecipitates from depleted and undepleted lysates were also assayed for PTP activity to determine the negative control values.