Selected cellular immune parameters were studied in 20 patients with sickle cell anaemia (SCA). A moderate absolute lymphocytes was observed in SCA patients compared with the control group. There was no significant difference between patients and controls in the mean E-rosette percentage and absolute number. PHA transformation was decreased in 50% of SCA patients, and some of them showed cutaneous anergy. It was suggested that impaired cell-mediated immunity is another factor to be included among defective SCA host-defense mechanism.

Circulating immune complexes were investigated in sera of 13 patients with paroxysmal nocturnal hemoglobinuria. A significant inhibition was observed in the complement-dependent rosette formation (EAC) in 6 cases; 2 patients presented an increased anti-complementary activity; antilymphocyte antibodies were demonstrated in 2 patients. The levels of C₃d and immunoconglutinins were also increased; there were no differences in the total hemolytic complement between patients and normal controls. There was a significant correlation between C₃d and immunoconglutinins with the inhibition of the EAC rosette formation test. These results provide evidence for the presence of circulating immune complexes in paroxysmal nocturnal hemoglobinuria.

14 patients with chronic myelocytic leukemia were evaluated immunologically; no difference was found in mean lymphocyte percentage and absolute number between patients and healthy subjects. 4 cases (28.5%) showed decreased percentage of T lymphocytes, while only 2 cases (14.2%) had decreased absolute T lymphocyte values. PHA transformation was decreased in 57% of the patients, Spontaneous transformation in the short-term cultures exceeded the normal range in 65% of the cases. All patients skin tested were found to be reactive. Most of the patients had defective cellular immune response in vitro, probably related with a qualitative defect in T lymphocyte subpopula-tions. It cannot be completely excluded that part of the observed lymphocyte depression was due to the busulfan.

Circulating immune complexes in sera from sickle cell anemia (SCA) patients were investigated using inhibition of complement-dependent lymphocyte rosette formation (EAC rosette inhibition) and the anticomplementary assay. A significant inhibition of EAC rosette formation was seen in seven (77%) sera from SCA patients with hepatic crisis. Four (44%) sera from these patients showed slightly increased anticomplementary activity. These preliminary results provide evidence for the presence of circulating immune complexes in some SCA patients with hepatic crisis.