Immunohistochemical HLA-DR antigen expression with lymphocyte subsets and proliferative activity in pterygium.

The immunohistochemical expression of HLA-DR antigen, CD8, CD4, CD68, S1OO, PCNA and Ki-67 was performed in order to investigate the role of immune mechanisms in pterygium, in correlation with proliferative activity. A series of 98 surgically-excised pterygia, 18 pingueculae and 20 normal conjunctivae, was studied by the avidin-biotin method, on formalin-fixed, paraffin-embedded tissue. HLA-DR antigen was abundantly expressed in pterygium epithelial cells, whereas almost no expression was found in pinguecula and normal conjunctiva. A high value of Ki-67 and PCNA expression coexisted in the same areas with HLA-DR antigen expression in pterygium and a statistically significant positive correlation resulted between them (p = 0.002). Aberrant infiltration of inflammatory cells (CD4, CD8, CD68, S100) was detected in pterygium, while lower densities were found in pinguecula and conjunctiva. The data suggest that immunopathological mechanisms may contribute in the pathogenesis of pterygium. In addition, the aberrant HLA-DR antigen expression seems to be correlated with the growth fraction of the lesion.