IL-4 induces conformational change of CD20 antigen via a protein kinase C-independent pathway. Antagonistic effect of anti-CD40 monoclonal antibody.
The CD20 molecule is a unique phosphoprotein exclusively expressed on B cells during most stages of B cell ontogeny. We here report that rIL-4 down-regulates the expression of CD20 with anti-Leu-16 mAb (clone L27) on both unstimulated and anti-mu preactivated normal and leukemic B cells. None of the other recombinant lymphokines tested (IL-1, IL-2, IL-3, IL-6, IFN-alpha, and IFN-gamma, granulocyte/macrophage-CSF, transforming growth factor-beta, TNF-alpha, and lymphotoxin) decreased CD20 expression. Incubation of unstimulated or anti-mu preactivated B cells with IL-4 did not affect the steady state CD20 mRNA, suggesting that IL-4 exerted its effect mainly at a nontranscriptional level. Hence, IL-4 selectively down-regulates the CD20 epitope recognized by clone L27 without affecting seven other different epitopes, indicating that IL-4 acts by modifying the conformation of the CD20 molecule rather than by inhibiting its production or inducing its internalization. IL-4 most likely utilizes a protein kinase C-independent signal transduction pathway to modify CD20 molecule inasmuch as staurosporine, an inhibitor of protein kinase C, antagonizes phorbol esters (PMA) but not IL-4-induced CD20 down-regulation. In contrast, anti-CD40 mAb reverses the IL-4 but not the PMA inhibitory effect on CD20 expression. Given that CD20 may be part of a Ca2+ ion channel and plays a role in B cell activation and proliferation, it is proposed that the ability of anti-CD40 mAb to maintain the CD20 molecule in a given epitopic configuration on IL-4-stimulated B cells may be related to the long term proliferation of normal B cells that are strictly dependent on the presence of IL-4 and cross-linked anti-CD40 mAb for their continuous growth.
Notre-Dame Hospital, Research Center, University of Montreal, Quebec, Canada.
M
M
Dancescu
C
C
Wu
M
M
Rubio
G
G
Delespesse
M
M
Sarfati
D000911:Antibodies, Monoclonal / Q000276:immunology*; D015703:Antigens, CD / Q000032:analysis* / Q000276:immunology / Q000502:physiology*; D018951:Antigens, CD20; D000944:Antigens, Differentiation, B-Lymphocyte / Q000032:analysis* / Q000276:immunology / Q000502:physiology*; D001483:Base Sequence; D019013:CD40 Antigens; D002478:Cells, Cultured; D015536:Down-Regulation; D006801:Humans; D015847:Interleukin-4 / Q000494:pharmacology*; D008969:Molecular Sequence Data; D011487:Protein Conformation / Q000187:drug effects; D011493:Protein Kinase C / Q000502:physiology*; D015398:Signal Transduction
D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D018951:Antigens, CD20; D000944:Antigens, Differentiation, B-Lymphocyte; D019013:CD40 Antigens; D015847:Interleukin-4; D011493:Protein Kinase C