The impact of elevated serum IgA and race on primary recipient renal allograft survival.

Abstract

This study correlated overall serum IgA levels in pretransplant (preTx) sera with graft survival. IgA levels, determined by nephelometry, were normally distributed, with a mean level of 255 +/- 139 mg/dl and a median of 234 mg/dl in 631 adult primary kidney allograft recipients and a mean level of 213 +/- 123 mg/dl with a median of 196 mg/dl for 100 retransplant recipients. Improved 3-year survival was associated with a high preTx IgA serum level in primary recipients (Kaplan-Meier analysis, P = 0.01), but not in retransplant patients. After stratifying by race, IgA correlated with graft survival in Caucasian, Hispanic, and "other" (Middle Eastern, Indian subcontinent, and Asian) primary recipients (P < or = 0.04), but not in African Americans. Higher survival rates were not associated with IgA in primary recipients stratified for rejection episodes, blood transfusions, or HLA-DR mismatches. Graft survival was improved in patients with > 2 HLA-AB mismatches and serum IgA above the median. PreTx IgA level and IgA alpha-HLA activity were significantly associated in preTx sera of primary renal allograft recipients (chi 2 = 7.145, P = 0.01), although only 9% (12/133) of sera tested displayed IgA anti-HLA class I reactivity. Thus, enhanced graft survival mediated by elevated serum IgA levels may due in part to competition for allograft HLA class I binding with deleterious Ig subclasses or immune effector cells. Elevated serum IgA may also reflect an altered immunoregulatory state. The results suggest that, depending on the racial group, preTx serum IgA levels are a prognostic indicator of graft survival in primary renal allograft recipients.