In each case, the major
arcs formed with these three antigens show a
reaction of identity. The identity of this as the B
protein was established by its characteristic position
on both immunodiffusion and immunoelectrophoresis
(11). Antiserum against rat VLDL produced
the B arc as well as three other arcs with
VLDL and two additional arcs with HDL. Two of
these arcs represent VLDL proteins which are also
present in HDL. One of the latter is also found in
the fraction of density greater than 1.21 g/cm ~.