CD33 as a leukocyte-associated marker expressed on human spermatozoa

OBJECTIVE: Sialic acid-binding immunoglobulin-type lectins (Siglecs) are commonly present on immune cells and often mediate cell-to-cell interactions and signaling. Studies have shown the presence of Siglecs 1, 2, 5, 6, 10 and 14 on human spermatozoa. To the best of our knowledge, the expression of CD33 on spermatozoa has not yet been studied. Semen samples were collected from 25 healthy men with normal semen status. CD33 expression on purified spermatozoa was evaluated by flow cytometry methods. RESULTS: The results demonstrate the expression of CD33 on the surface of purified spermatozoa. The mean (± SD) of MFI (mean fluorescence intensity) was 12.85 (± 1.33) and the mean percentage of spermatozoa that express CD33 was 73.75 (± 3.75). Results were obtained showing that spermatozoa express CD33 (or Siglec-3) on their surface. The physiological role of these molecules on spermatozoa remains to be determined. It is recommended that further research be undertaken regarding the role of Siglecs (such as CD33) on spermatozoa apoptosis.