Isolation of a VHClambda fragment on tryptic digestion of human IgD myeloma proteins.

The tryptic digestion pattern of IgD myeloma proteins is reported. The Fab delta of fragment is shown to be very susceptible to further degradation to yield a novel fragment composed of VH and Clambda domains which are still bound through the interchain disulphide bridge. Reduction results in a change in M.W. from ca. 26,000 to 13,000. The loss of Fd delta of isotypic determinants may be of importance to studies in which membrane bound IgD is detected or measured after release from the cell surface by enzyme digestion.