Similar experiments were performed in seven patients with monoclonal
S.IgG. In three cases with IgG K (including two with a monoclonal serum
IgG K) the lymphocytes synthetized y and K determinants in vitro. Similarly,
IgG A was shown to be a cell product in two of four cases with S.IgG A.
In contrast, when lymphocytes from the two other patients (one of whom
had a monoclonal serum IgG A) were incubated in culture medium after
removal of the S.IgG A, y determinants were no longer detectable and the
cells carried newly synthetized p. and A chains. When freshly drawn cells
from these two patients were labeled by antiserum to ‘‘ chains and subsequently
warmed, cap formation occurred on most lymphocytes and previously
undetected p. chain determinants were found by double labeling all around
the cell surface except at the site of the cap.