Beyond HLA: an exploratory pilot study of non-HLA antibodies, HLA sensitization, and GSTT1 genotype in platelet...

Platelet transfusion refractoriness (PTR) is a common and clinically challenging condition with complex underlying mechanisms. Human leukocyte antigen (HLA) alloimmunization is the principal cause of immune PTR (iPTR), whereas non-HLA antibodies (non-HLA Abs) are known to contribute to antibody-mediated rejection, microvascular inflammation, interstitial fibrosis, and graft loss. However, whether non-HLA Abs contribute to the development of PTR and how they are associated with HLA alloimmunization remain unclear.

This retrospective study evaluated the expression profiles of 60 non-HLA Abs and the degree of HLA alloimmunization in 32 patients with PTR and 20 healthy blood donors using a multiplex Luminex single-antigen bead assay. GSTT1 gene deletion status in this cohort was determined by quantitative PCR (qPCR). Risk factors associated with the development of non-HLA Abs in PTR patients were analyzed using multivariable logistic regression with penalized maximum likelihood estimation (Firth correction).

The overall positivity rate of non-HLA Abs in PTR patients was significantly higher than that in healthy blood donors (90.63% vs. 55%, p = 0.006). Among the 14 positive non-HLA Abs tested, none showed statistically significant differences in odds ratios (ORs) between the non-iPTR and iPTR groups. Compared with healthy donors, only the positivity rates of CSF2 Ab and GSTT1 Ab were significantly increased in the non-iPTR and/or iPTR groups. A history of multiple transfusions was strongly associated with overall non-HLA Ab positivity, as well as with CSF2 Ab and GSTT1 Ab positivity (OR = 6.12, p = 0.008; OR = 21.9, p = 0.001; OR = 12.56, p = 0.017). Overall, 26 of 52 individuals (50%) across all groups exhibited homozygous deletion of the GSTT1 gene (GSTT1*0/0), among whom 34.62% (9/26) developed GSTT1 Ab. Among PTR patients with GSTT1*0/0, 56.25% (9/16) were positive for GSTT1 Ab. In contrast, no GSTT1 Ab were detected in healthy donors, although 45% (9/20) had a history of pregnancy.

In this exploratory pilot study, non-HLA antibody profiles were independently correlated with PTR beyond HLA sensitization, with multiple transfusions as a clinically relevant factor linked to CSF2 and GSTT1 Abs, whereas the GSTT1*0/0 genotype appeared to be a prerequisite for the formation of GSTT1 Abs. Whether incorporating non-HLA antibody screening and GSTT1 genotyping into pre-transfusion evaluation can improve precision transfusion remains to be validated in prospective studies.