Cytochemical localisation of acid phosphatase in the phagocytising conjunctival epithelium of the guinea pig.

The ultrastructural localisation of acid phosphatase activity was investigated on the guinea pig conjunctival epithelium incubated in vivo with a suspension of latex spheres. Deposits of acid phosphatase reaction product were concentrated on the elements of GERL, the phagocytic vacuoles, and the cell membrane. Acid phosphatase activity in GERL was intense in basal and suprabasal cells and decreased towards the superficial cells. Phagosomes containing latex spheres and reaction product of acid phosphatase were observed mainly in the centrospheral region of the superficial and intermediate epithelial cells. Acid phosphatase activity in phagocytising cells was not increased as compared to that in non-phagocytising cells. The observations indicate that existing acid phosphatase in unstimulated conjunctival epithelial cells is released into heterophagosomes brought within the lysosomal compartment. The number of secondary phagosomes seems to be increased by intercellular transport of latex spheres to the acid phosphatase rich cells in the deep layers of the epithelium.