Studies on the Fc receptors and masking substances on mouse and rat myeloma cells.

Abstract

Mouse and rat myeloma cell lines showed little or no rosette formation with sheep erythrocytes (SRBC) coated with rabbit IgG (rabbit EA) but showed marked rosette formation after treatment with trypsin, pronase or neuraminidase. These cell lines showed no rosette formation with SRBC coated with mouse IgG (mouse EA): treatment with trypsin enabled the detection of rosettes among the mouse myeloma cell lines but not by the rat myeloma cells. The F(ab')2 fragment of the anti-Fc receptor II antibody blocked the formation of rosettes with rabbit EA by mouse myeloma cell lines after treatment with trypsin. Aggregated mouse IgG1 and IgG2b subclasses strongly inhibited the formation of rosettes with rabbit EA, whereas aggregated mouse IgG2a showed a marginal inhibitory effect. A large amount of mouse IgG2a, however, caused significant inhibition. Our results also revealed that aggregated mouse IgG could bind to the rat myeloma cell line. The Fc rosette forming abilities of the enzyme-treated mouse and rat myeloma cells became reduced after cultivation both in the presence and absence of FCS but not after cultivation in the presence of cycloheximide, suggesting that cell surface substances, which may be glycoprotein that incompletely mask Fc receptors, are produced by myeloma cells.