The human (PsiL+mu-) proB complex: cell surface expression and biochemical structure of a putative transducing receptor.
The surrogate light chain (PsiL) associates with mu and Igalpha-Igbeta chains to form the preB-cell receptor that plays a critical role in early B-cell differentiation. Discrepancies exist in human concerning the existence of PsiL+mu- proB cells and the biochemical structure of such a proB-cell complex remains elusive. Among new antihuman VpreB monoclonal antibodies (MoAbs), 5 of the gamma kappa isotype bound to recombinant and native VpreB protein with high affinity. They recognized 4 discrete epitopes, upon which 2 were in the extra-loop fragment. Such MoAbs detected the PsiL at the cell surface of either preB or on both proB and preB cells. The previously reported SLC1/SLC2 MoAbs recognize a conformational epitope specific for the mu/PsiL association in accordance with their preB-cell reactivity. Using the proB/preB 4G7 MoAb, PsiL cell surface expression was detected on normal bone marrow, not only on CD34(-)CD19(+) preB but also on CD34(+)CD19(+) proB cells. Futhermore, this MoAb identified PsiL+mu- fresh proB leukemic cells of the TEL/AML1 type. Biochemical studies showed that, at the proB stage, the PsiL is associated noncovalently with two proteins of 105 and 130 kD. Triggering of this complex induces intracellular Ca2+ flux, suggesting that the PsiL may be involved in a new receptor at this early step of the B-cell differentiation.
Lemmers
B
B
Centre d'Immunologie de Marseille-Luminy, Marseille, France.
Gauthier
L
L
Guelpa-Fonlupt
V
V
Fougereau
M
M
Schiff
C
C
D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D000918:Antibody Specificity; D018941:Antigens, CD19 / Q000032:analysis; D018952:Antigens, CD34 / Q000032:analysis; D001402:B-Lymphocytes / Q000276:immunology*; D001854:Bone Marrow Cells / Q000276:immunology; D002462:Cell Membrane / Q000276:immunology*; D005434:Flow Cytometry; D006801:Humans; D007147:Immunoglobulin Light Chains; D054444:Immunoglobulin Light Chains, Surrogate; D007148:Immunoglobulin mu-Chains / Q000737:chemistry* / Q000235:genetics* / Q000276:immunology; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000235:genetics* / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D015452:Precursor B-Cell Lymphoblastic Leukemia-Lymphoma / Q000276:immunology; D011994:Recombinant Proteins / Q000276:immunology; D013234:Stem Cells / Q000276:immunology
D000911:Antibodies, Monoclonal; D018941:Antigens, CD19; D018952:Antigens, CD34; D007147:Immunoglobulin Light Chains; D054444:Immunoglobulin Light Chains, Surrogate; D007148:Immunoglobulin mu-Chains; D008562:Membrane Glycoproteins; D011994:Recombinant Proteins