THE CD5(+) B-CELLS AND MYASTHENIA-GRAVIS

A high frequency of CD5(+)B lymphocytes in the peripheral blood of pat ients with myasthenia gravis (MG) has been reported recently. These re sults seem to indicate an attractive linkage between CD5(+)B lymphocyt es and autoantibodies against Acetylcholine receptor in MG. We examine d the frequency of CD5+B cells in 20 patients with MG and 21 normal he althy controls by two-color flow cytometry. However, there were no sig nificant differences in the percentages of CD5(+)B lymphocytes between the two groups. We also examined the frequency of CD5(+)B lymphocytes in the resected thymus of patients. The frequency of CD5(+)B lymphocy tes in the thymus was low and similar pattern to that in the periphera l blood. We checked the antibody (Ab) production against the human ace tylcholine receptor in either CD5(+)B or CD5(-)B lymphoctes using B ly mphoblastoid cell line generated from the lymphocytes of 11 patients w ith anti-AChR Abs in the sera. Abs against the AChR in the human were mostly produced by CD5(-)B, not CD5(+)B lymphocytes. The anti-AChR Abs (IgG) production of CD5(+)B cells and CD5(-)B cells (mean +/- SD) wer e 6.8 +/- 2.4 fmol/ml and 18.5 +/- 17.6 fmol/ml, respectively. These r esults sugget that in MG, the frequencies of the CD5(+)B lymphocytes i n PBL may be genetic background and that there may be no strong linage s between AChR Ab production and CD5(+)B lymphocytes.