Molecular Interactions of Helper T Cells and APC CD4+T Cell CTLA-4 CD28 p56 Ick CD3 CD2 TCR LFA-1 CD45 几A-1 peptide B7 CD4 MHC II LFA-3 ICAM-1 Collagen CD80/CD86 CD40 APC/B cell L.Chess 2002   e V C C V z z p56 lck peptide CD3 CD28 CD40 LFA-3 LFA-1 MHC II ICAM-1 B7 CD40L CD4 CD45 TCR CD2 CD4+ T Cell APC/ B cell h h Molecular Interactions of Helper T Cells and APC B7 CTLA-4 VLA-1 Collagen CD80/CD86 L. Chess 2002