Enumeration of human B lymphocytes in stained blood smears by their binding of bacteria

Abstract

Human B lymphocytes were enumerated in stained blood smears by two methods. In one method, the surface Ig of B cells was detected by the antibody-mediated binding of anti-light chain antibody-coated Escherichia coli (anti-Ig Ab- E. coli). By using only anti-κ or anti-λ antibody-coated E. coli or a mixture of both, the number of κ-bearing, λ-bearing, and total Ig-bearing lymphocytes was determined. Lymphocytes were found to bear only κ or λ light chains (but not both), indicating that B cells do not normally have passively adsorbed Ig on their surface. The second method was based on the property of a strain of Brucella melitensis (Bm) to bind to human B lymphocytes. This was shown by the fact that Bm and anti-Ig Ab- E. coli bind to the same cells, i.e., B cells. Competition experiments suggested that the binding of Bm to the B cells was not via the surface Ig of the B cells. The number of B cells in the peripheral blood of several normal donors and several patients with chronic lymphocytic leukemia is presented. The use of bacteria to label the B cells in blood smears allows for the morphological identification of lymphocytes and eliminates the need to purify the lymphocytes, thereby also eliminating the problem of the selective loss of T or B cells during the purification. By using this method the enumeration of the κ-bearing, λ-bearing, and total number of human B cells may become a routine diagnostic procedure.