[Lymphocytic subpopulations implicated in the rheumatoid rosette phenomenon].

The significance of the phenomenon of rheumatoid rosettes (RR) was studied in 21 subjects suffering from rheumatoid polyarthritis (RP) and in 16 controls. Certain technical factors influenced the prevalence of RR. Thus the number of RR increased in the RP patients and the controls with increase in the number of sensitized 0 Rhesus - red corpuscules; nevertheless there was a significant difference between the results obtained with the RP patients and the controls. The length of incubation and the temperature played an important role: prolonged contact times (30 min to one night), particularly at 4C considerably increased the numbers of RR, which reached 10 per cent both, in the controls and in the RP patients. The separation of lymphocytes by filtration through nylon according to Greaves' technique was followed by a study of the T cells (E rosettes), the B cells (surface immunoglobulins), and the RR. In all cases (RP and controls), the numbers of RR increased after filtration through nylon which retained the B cells. Separation of the lymphocytes by the centrifuging of the E rosettes showed that the proportion of RR was clearly higher in a population rich in B lymphocytes and lower in a population rich in T lymphocytes. Futhermore, filtration through nylon of cell suspensions rich in B lymphocytes showed a considerable rise in the RR and parallel drop in the number of B cells. Reduction of the RR by centrifuging did not affect the numbers of T or B cells. In the light of these results, it seems that the cell responsible for the formation of the RR does not have the characteristics of either the T or the B lymphocytes: a lymphocyte carring a receptor for the fragment Fc of the immunoglobulins (K cells) could be involved. In this case, the RR should be related to the EA rosettes of which they perhaps represent and active fraction.