Presence and possible significance of immunohistochemically demonstrable metallothionein expression in pterygium versus pinguecula and normal conjunctiva

Purpose To investigate metallothionein (MT) expression in pterygium, pingue cula and normal conjunctiva and define its possible significance in this ar ea of the eye. In order to further elucidate the mechanism of MT expression we correlated it with lymphocyte subpopulations (T4, T8), macrophages (CD6 8), Langerhans' cells (S100) and the proliferation-associated indices (PCNA , Ki67). Methods Eighty-five surgically excised pterygia, 15 pingueculae and 20 norm al conjunctivae were immunohistochemically studied by the avidin-biotin (AB C) method. A monoclonal antibody (E9) against a conserved epitope of I and II isoforms of MT was used on formalin-fixed, paraffin-embedded tissues. St atistical analysis was performed using the SPSS statistical package. Results Epithelial MT expression was detected in all 120 cases examined and in most of them both nuclear and cytoplasmic immunoreactivity was present. Nevertheless no statistically significant difference of MT expression was found between the three types of tissue. A statistically significant positi ve correlation between MT expression and lymphocyte subsets, macrophages an d Langerhans' cells was found in pterygium. On the contrary, we did not fin d any statistical correlation in pinguecula and normal conjunctiva. In all three types of tissues MT expression was also positively correlated with th e proliferation-associated indices. Conclusion The data suggest that there is immunohistochemically demonstrabl e MT expression in the epithelium of pterygium, but also of normal conjunct iva and pinguecula. MT may serve a photoprotective role in this region. In pterygium in particular, the biochemical pathway of MT synthesis seems inte restingly to cross the pathways of cell proliferation, inflammation and imm une activation.