STUDIES OF SPERM-LYMPHOCYTE INTERACTION STRUCTURES

We have discovered that human sperm can rapidly bind and
penetrate human lymphocytes in vitro. These interactions are
selective for cells bearing surface HLA class II molecules, and
data for antibody inhibition studies suggest that the lymphocyte
surface receptor for sperm is the HLA-DR molecule, while the
corresponding sperm recognition ligand may be a structure similar
to T cell surface T4. Two goals are set for the upocoming project
period. These are: (1) to identify the sperm surface T4-
crossreactive ligand and to define its role in recognition of
lymphocyte surface HLA-DR, and (2) to test for a role for sperm-
lymphocyte interactions in the sexual transmission of AIDS. Sperm-blood cell interactions in humans may reflect the presence
on blood cells of molecules similar to the sperm receptors on the
egg envelopes. Definition of a role for the MHC glycoproteins
and the Ig-related T4 molecule in human sperm-lymphocyte
interactions, therefore, provides the first evidence for a
relationship between gametic and somatic self-recognition
systems in higher chordates. These studies grew out of our work with marine protochordates,
which has been directed toward studies of the early evolution of
the related major histocompatibility complex (MHC) and
immunoglobulin (Ig) multigene families. In the colonial tunicate
Botryllus, we have defined an MHC-like histocompatibility gene
system that controls both graft rejection and fertilization
between colonies. This condition may be common to all tunicates;
interactions between co-cultured sperm and blood cells of the
solitary tunicate Ciona, like the intercolony graft rejections in
Botryllus, follow the established genetics of mating type. The
occurrence of specific sperm-lymphocyte interactions in humans,
and the apparent involvement of MHC class II structures and the
Ig-related T4 molecule in these events, thus adds to the evidence
for homology between the protochordate and vertebrate major
hisotcompatibility genes.