Ly-1 (CD5), a membrane glycoprotein of mouse T lymphocytes and a subset of B cells, is a natural ligand of the B cell surface protein Lyb-2 (CD72).
CD5 is a 67-kDa glycoprotein expressed on the cell surface membrane of all T lymphocytes and on a small proportion of B lymphocytes. The physiologic role of this Ag is still unknown. Structural and functional studies of CD5 suggest that it might act as a receptor for a positive signal. CD5-specific mAb augment CD3- or mitogen-induced T cell proliferation, IL-2 secretion, and IL-2R expression and induce a rise in intracellular [Ca2+]. In this report, we describe the purification of mouse CD5 protein (mCD5) and its use as a probe to search for the ligand of CD5. We demonstrate that mCD5 specifically interacts with the mouse B cell differentiation Ag CD72/Lyb-2. Three serologically defined allelic forms of mouse CD72/Lyb-2 can all interact with mCD5. We further show that mCD5 can interact with human CD72/Lyb-2, and similarly, that human CD5 can interact with mouse CD72/Lyb-2. These studies may have major implications for the mechanisms of T-B cell communication.
Division of Hematology-Immunology, Medical School, Vrije Universiteit Brussel, Belgium.
W
W
Luo
H
H
Van de Velde
I
I
von Hoegen
J R
JR
Parnes
K
K
Thielemans
D000818:Animals; D015703:Antigens, CD / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D000944:Antigens, Differentiation, B-Lymphocyte / Q000235:genetics / Q000378:metabolism*; D000945:Antigens, Differentiation, T-Lymphocyte / Q000378:metabolism; D000950:Antigens, Ly / Q000378:metabolism*; D001402:B-Lymphocytes / Q000166:cytology*; D018956:CD5 Antigens; D006801:Humans; D008024:Ligands; D008562:Membrane Glycoproteins / Q000378:metabolism; D051379:Mice; D011485:Protein Binding; D011994:Recombinant Proteins / Q000378:metabolism; D013045:Species Specificity; D013601:T-Lymphocytes / Q000166:cytology*
D015703:Antigens, CD; D000944:Antigens, Differentiation, B-Lymphocyte; D000945:Antigens, Differentiation, T-Lymphocyte; D000950:Antigens, Ly; D018956:CD5 Antigens; C064228:CD72 protein, human; D008024:Ligands; D008562:Membrane Glycoproteins; D011994:Recombinant Proteins