Introduction: workshop summary of the CD15 monoclonal antibody panel from the Fifth International Workshop on Leukocyte Antigens.

CD15 is expressed on a wide variety of tumor cells including myeloid leukemia, breast, colorectal, lung cancer cells. It is probable that the core proteins and lipids differ on the different cell types since there is marked variability in the binding of the mAb within and among the different cell types. Previously, there had only been a single mAb of the IgG class directed to CD15. The present study demonstrates the existence of one more IgG mAb (an IgG3). Unfortunately, a third mAb submitted as an IgG1, MA14, did not appear to be an IgG in our studies and a fourth mAb, MA9, submitted as an IgG1 did not have significant binding activity and also could not be confirmed as anti-CD15. An interesting finding was that all of the mAb could mediate complement-dependent cytotoxicity with rabbit serum. However, the two IgG3 mAb, MA63 (MCS-1) and MA88 (7C3), could not mediate lysis with human complement, while all of the IgM mAb could do so. It is not clear why this difference exists. CD15 is known to be expressed on mature myeloid cells in the hematopoietic lineage. The expression of CD15 on progenitor cells has been mapped by the indirect method of C'-dependent lysis and measurement of colony-forming cells. These studies have estimated that about 50% of normal CFU-GM express CD15. In the present workshop, we examined the expression of CD15 on a quantifiable cell population, the CD34 positive population.(ABSTRACT TRUNCATED AT 250 WORDS)