Allogeneic B Cell Response to H-Y Minor Histocompatibility Antigens after Donor Lymphocyte Infusion Correlates with Disease Response.

Donor lymphocyte infusion (DLI) can induce remission in many patients who relapse after allogeneic hematopoietic stem cell transplantation (HSCT). We have previously demonstrated that male HSCT patients with female donors frequently develop high-titer antibody responses to H-Y antigens that correlate with disease remission. DLI administered 6 months after T cell depleted HSCT results in a five-fold increase in peripheral B cell numbers. We sought to determine whether allogeneic B cell responses develop after DLI. We expressed 5 recombinant H-Y proteins (DBY, UTY, ZFY, RPS4Y and EIF1AY) and developed sensitive ELISA to quantify the development of specific anti-HY antibodies. First, we studied prophylactic DLI. Twenty-six patients who received T cell depleted HSCT followed 5–7 months later by prophylactic CD8 depleted DLI were tested for H-Y antibodies pre-DLI and 6–12 months after DLI. No H-Y antibodies were detected in any of the pre-DLI serum samples. However, all 6 male HSCT patients with female donors (F→M HSCT) developed high-titer antibodies against at least one H-Y antigen after DLI. In contrast, only 1/20 of the other donor/recipient gender combinations (4 M→M, 8 F→F, 8 M→F) resulted in H-Y antibody (p<0.005). Thus, mHA disparity is required for the development of allogeneic B cell responses after DLI. This robust development of H-Y antibody in 6/6 F→M patients who received TCD transplantation and prophylactic DLI was significantly greater than 3/9 who developed H-Y antibodies after receiving the same TCD HSCT without DLI (p=0.03). This suggests that DLI augments allogeneic B cell responses after T cell depleted HSCT. To examine the effects of therapeutic DLI, we studied 24 F→M HSCT patients who relapsed 60 days to 15 years (median 704 days) after transplant and subsequently received either unmanipulated DLI (1−3x107 CD3+ cells/kg; n=12) or CD8 depleted DLI (3x107 CD4+ cells/kg; n=12). Only 2/24 had any H-Y antibody at the time of relapse. After DLI, 17/24 (71%) developed antibody to at least one H-Y antigen, and this correlated with complete remission after DLI (p<0.001). Disease progression continued in all 7 patients who did not develop H-Y antibodies, but 15 of 17 patients who developed H-Y antibodies also attained complete remission. H-Y antibodies developed rapidly and were detected as early as 26 days after DLI. Fifteen of 17 patients (88%) became H-Y antibody positive before 150 days after DLI. In our previous study assessing HSCT alone, only 3 of 38 (8%) developed H-Y antibodies before 150 days. Complete remission was attained with similar frequencies after both CD8 depleted DLI (7/12) and unmanipulated DLI (8/12). However, significant differences were noted in H-Y antibody responses by DLI type. In contrast to unmanipulated DLI, patients receiving CD8 depleted DLI developed high-titer antibodies (p=0.045) against multiple H-Y antigens (p=0.012). In summary, H-Y antibodies frequently develop in male patients after infusion of female donor lymphocytes and this allogeneic B cell response correlates with clinical response to DLI. H-Y Antibody Results in Male Patients with Female Donors Any H-Y Antibody 2 or more H-Y Antibodies TCD HSCT + prophylactic CD8 depleted DLI 6/6 (100%) 4/6 (67%) TCD HSCT alone 3/9 (33%) 1/9 (11%) CD8 depleted DLI for relapse 9/12 (75%) 9/12 (75%) Unmanipulated DLI for relapse 8/12 (67%) 2/12 (17%)