title: Differential modulation of human multinegative (CD3-4-8-) thymocyte proliferation by monoclonal antibodies to CD45RA or to CD45.
abstract: Human multinegative (CD3-4-8-19-; MN) thymocytes proliferate optimally in response to anti-CD2 plus anti-CD28 mAb plus PMA or IL-7. The role of CD45 was assessed by the addition of mAb to a CD45 common determinant, or to CD45RA. MN thymocytes are unresponsive to anti-CD2 mAb. Co-stimulation with anti-CD45RA generated 1.6-5.7-fold enhancement of a proliferative response, with maximal enhancement by cross-linkage of CD45RA molecules. The response to anti-CD2/28 mAb was reproducibly enhanced only by immobilized anti-CD45RA. Cross-linking of CD45RA and CD28 through the use of heteroconjugates of mAb did not enhance the co-stimulation by CD45RA. The most marked enhancement by anti-CD45RA occurred in suboptimal activation conditions. In contrast, the response to anti-CD2 or anti-CD2/28 was inhibited by mAb to CD45 common determinants (anti-CD45) in the presence or absence of PMA or IL-7, with the most profound inhibition (6-8-fold) detected in optimal proliferative conditions. Cross-linking of CD45 and CD28 through heteroconjugates of mAb was required as soluble anti-CD45 or immobilized anti-CD45 were unable to mediate inhibition. This inhibitory effect of (anti-CD45 x 28) was specific to MN thymocytes as no inhibition was detectable when peripheral blood T cells were treated with anti-CD2/28 and the same heteroconjugate. The differential effects of anti-CD45 and anti-CD45RA may reflect either CD45 heterogeneity on MN thymocytes, or the physical modulation of a single CD45 molecules by interactions at different epitopes, and the avidity of the relevant CD45 mAb for thymocyte CD45 isoforms may play a role.(ABSTRACT TRUNCATED AT 250 WORDS)
authors: Department of Immunology, University of Alberta Edmonton, Canada.
authors: J P
authors: JP
authors: Deans
authors: J A
authors: JA
authors: Ledbetter
authors: L M
authors: LM
authors: Pilarski
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology* / Q000494:pharmacology; D018106:CD28 Antigens / Q000502:physiology; D002648:Child; D006801:Humans; D017493:Leukocyte Common Antigens / Q000276:immunology* / Q000502:physiology; D008213:Lymphocyte Activation; D011994:Recombinant Proteins / Q000378:metabolism; D015203:Reproducibility of Results; D015398:Signal Transduction; D016176:T-Lymphocyte Subsets / Q000378:metabolism*; D013950:Thymus Gland / Q000166:cytology*
chemical_list: D000911:Antibodies, Monoclonal; D018106:CD28 Antigens; D011994:Recombinant Proteins; D017493:Leukocyte Common Antigens