Conjugate formation between cells expressing SIRPβ2 and CD47. (A) BW-SIRPβ2 transfectants make conjugates with Jurkat but not with Jurkat-CD470. Conjugation is partially blocked by anti-CD47 and anti-SIRP antibodies, whereas no significant inhibition is observed with an antibody against CD18 (β2 integrin). Percentages of conjugates are indicated next to the upper right quadrants. BW-SIRPβ2 was labeled with CFSE. Jurkat and Jurkat-CD470 were stained with anti-CD45-allophycocyanin. (B) The frequency of conjugation between Jurkat alone (top panel), Jurkat and JurkatCD470 (bottom panel), and Jurkat-CD470 alone (middle panel). Jurkat-CD470 forms fewer conjugates with itself than when mixed with Jurkat, and fewer than Jurkat forms with itself. Jurkat and Jurkat-CD470 were stained with Vibrant and CFSE before conjugation. Notably, Jurkat-CD470 cells express higher levels of SIRPβ2 than Jurkat cells (top histograms, gray profiles). This high expression of SIRPβ2 may allow Jurkat-CD470 cells to form as many conjugates with Jurkat cells as Jurkat forms with itself.
