The CD5/CD72 receptor system is coexpressed with several functionally relevant counterstructures on human B cells and delivers a critical signaling activity.
The CD5 molecule is expressed on T cells and, at a lower density, on a minor B cell subset (CD5+ B cells). The pan-B Ag CD72 was recently identified as the CD5 counterstructure, and several data suggest the involvement of this ligand pair in T-B cell cognate interaction. However, the functional role of CD5 and CD72 molecules within the B cell compartment is still unknown. In this work we studied umbilical cord blood CD5+ B cells (B-1a), adult splenic CD5- B cells (B-2), and CD5+ B cells from patients with chronic lymphocytic leukemia. Flow cytometry analysis and proliferation assays were used to determine 1) the ability of B-1a and B-2 cells to coexpress functionally relevant counterligands other than CD5 and CD72, and 2) the signaling capacity of CD5 and CD72 in terms of B cell activation and proliferation. To this purpose, freshly isolated or preactivated normal and neoplastic B cells were cultured with agonistic anti-CD5 or anti-CD72 mAbs in the presence or the absence of cytokines equipped with B cell activity. Our data demonstrate that CD5 and CD72 molecules are coexpressed with other ligand pairs usually involved in T-B cell cognate interaction on B-1a cells, but not on B-2 cells. CD5 and/or CD72 engagement delivers critical costimulatory signals in B-1a, B-2, and B cells from patients with chronic lymphocytic leukemia, but with different requirements and patterns. Besides suggesting the potential involvement of B-1a lymphocytes in B-B cell interactions during T-independent B cell responses, our results indicate that CD5 and CD72 counterstructures play a functional role in the B cell compartment.
Cerutti
A
A
Department of Clinical and Experimental Medicine, Padua University School of Medicine, Italy.
Trentin
L
L
Zambello
R
R
Sancetta
R
R
Milani
A
A
Tassinari
C
C
Adami
F
F
Agostini
C
C
Semenzato
G
G
D000328:Adult; D000368:Aged; D015703:Antigens, CD / Q000502:physiology*; D000944:Antigens, Differentiation, B-Lymphocyte / Q000502:physiology*; D016175:B-Lymphocyte Subsets / Q000378:metabolism*; D018956:CD5 Antigens / Q000502:physiology*; D016207:Cytokines / Q000502:physiology; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D015448:Leukemia, B-Cell / Q000378:metabolism; D008213:Lymphocyte Activation / Q000187:drug effects; D008297:Male; D008875:Middle Aged; D011947:Receptors, Antigen, B-Cell / Q000096:biosynthesis* / Q000502:physiology*; D015375:Receptors, Interleukin-2 / Q000378:metabolism; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism; D015398:Signal Transduction / Q000276:immunology*; D014407:Tumor Cells, Cultured
D015703:Antigens, CD; D000944:Antigens, Differentiation, B-Lymphocyte; D018956:CD5 Antigens; C064228:CD72 protein, human; D016207:Cytokines; D011947:Receptors, Antigen, B-Cell; D015375:Receptors, Interleukin-2; D018124:Receptors, Tumor Necrosis Factor