Soluble HLA class I molecules in malignant pleural and peritoneal effusions and its possible role on NK and LAK cytotoxicity.

PURPOSE

To examine the amount of sHLA-I in malignant pleural and peritoneal effusions and its possible role in natural immune defense.

METHODS

Three groups of patients (75 patients with malignancy, 21 with infection, and 27 with other diseases) were studied for sHLA-I value using an ELISA method. Cytolytic activity of freshly isolated pleural and peritoneal effusion-associated lymphoid (EAL) cells from 14 of cases with malignancy were examined and compared to that of ten non-cancerous patients. EAL cells were co-cultured with the autologous cell-free effusions immediately after collection and 3 days after incubation with IL-2.

RESULTS

The mean value of sHLA-I in effusions was 1.01+/-1.36 micro g/ml, 0.97+/-1.20 micro g/ml, and 0.49+/-0.45 micro g/ml, respectively. Despite higher mean sHLA-I levels in malignant and infected patients, no significant difference between these groups was observed ( P >0.05). Generally, the amount of sHLA-I in peritoneal effusions was higher than that for pleural effusions, but the difference was not significant. There were also no statistical differences in the sHLA-I levels between sub-groups of patients with malignancy. EAL cells' killing activity in malignant and infected effusions was 68.15+/-11.73 and 78.28+/-14.41, respectively ( P=0.08). No correlation between sHLA-I level and NK activity of EAL cells from the patients was found. Almost all malignant cases after exposure to cell-free effusions displayed an increase in NK activity (from 68.66+/-11.13 to 74.2+/-12.39, P=0.042) and a decrease in LAK activity (74.5+/-18.30 vs 67.72+/-16.46, P=0.040). Whereas, the same experiment performed for non-malignant effusions showed a decrease in both NK activity and LAK activity. Changes in NK and LAK activity were not correlated with the amount of sHLA-I in the effusions.

CONCLUSION

The presence of sHLA-I, particularly in malignant effusions, suggests a role for these molecules in tumor immunity in the peritoneal or plural environment; however, at least with these group of patients, sHLA-I appears not to be a unique determining factor on EAL cells' killing activity.