The CD19 antigen (95kDa) is expressed from the earliest stage of B progenitor development, on all
peripheral B cells including germinal centre B cells, and all B cell lines and B cell leukaemia
tested. T cell and monocytic cell lines are negative and the antigen is lost on B cell maturation
to plasma cells. The antigen is a type I integral membrane glycoprotein whose in vitro inhibition
will influence B cell activation and proliferation.