Mechanism of the LAI test in bladder cancer patients.

To clarify the mechanism of the leukocyte adherence inhibition (LAI) test, 30 bladder cancer patients were studied by the fractionated LAI test in which peripheral lymphocytes were separated into monocyte rich and monocyte deplete fractions. The mean LAI reactivity of 30 bladder cancer patients on the monocyte rich fraction (43.2 +/- 20.3 per cent) was significantly higher than that of the corresponding patients on the standard LAI test (30.4 +/- 12.7 per cent), whereas the mean LAI reactivity of these patients on the monocyte deplete fraction (15.6 +/- 10.7%) was significantly lower than that on the standard LAI test of the same patients (respectively p less than 0.001 and p less than 0.01). It suggests that monocytes play an important role in the capillary LAI test. To further comprehend the mechanism of the LAI phenomenon, indicator cells involved in the LAI test were observed by transmission and scanning electron microscopy. The microvilli on the cell surface of nonadherent monocytes of bladder cancer patients were decreased in number and shortened in length but other populations of nonadherent cells were not remarkably changed. These observations showed that the bladder tumor antigens in extracts from tumors appear to have an influence on the microvilli of monocytes, specifically on monocytes from bladder cancer patients. These morphological changes correlate with the results from fractionated LAI assay and may result in the tumor antigen specific LAI reactivity observed in leukocytes of bladder cancer patients.