Fetal hemoglobin in sickle cell anemia: relationship to erythrocyte adhesion markers and adhesion

To assess whether fetal hemoglobin (HbF) modulates the adhesion of sickle e rythrocytes to endothelium, children with homozygous sickle cell anemia (SS disease) were studied, using this physiologically crucial period to evalua te the relationships between HbF and the major erythrocyte adhesion markers . The mean level of CD36(+) erythrocytes was 2.59% +/- 2.15% (+/- SD, n = 4 0) with an inverse relationship be tween CD36 positivity and F cells (R = - 0.76, P < .000 00 002). In univariate analyses, significant correlations wi th various hematologic parameters and age were noted. Multiple regression a nalyses, however, revealed a relationship solely with F cells. Minimal leve ls of very rate activation antigen-4(+) (VLA4(+)) erythrocytes (0.31% +/- 0 .45%, n = 40) with relationships similar to those noted for CD36(+) cells w ere also observed. The subpopulation of strongly adhesive stress reticulocy tes was further assessed, using CD71 as their marker. The mean level of CD7 1(+) erythrocytes was 5.81% +/- 4.21%, with statistical correlates in univa riate and multivariate analyses similar to those discussed above. When adhe sion ratios were evaluated, inverse correlations were noted between basal a nd plasma-induced adhesion and F-cell numbers (R = -0.54, P < .0005; R = -0 .53, P < .0006, n = 39). In addition, in analyses where basal or plasma-ind uced adhesion was the dependent variable and the independent variables incl uded F cells and the various adhesion-related parameters, significant relat ionships solely with F cells were noted. The results demonstrate that SS pa tients with higher levels of F cells have concomitant decreases in the numb ers of CD36(+), VLA4(+), and CD71(+) erythrocytes and that these findings t ranslate into less adherent erythrocytes. These findings extend knowledge r egarding the protective effects of HbF in the pathophysiology of sickle cel l disease. (Blood, 2001;97: 2568-2573) (C) 2001 by The American Society of Hematology.