Adhesion of normal and neoplastic lymphoid cells to fibroblasts

CD45 partially mediates heterotypic adhesion between murine leukemia/lymphoma cell line L5178Y and marrow stromal cells

We raised mAbs to whole L5178Y leukemia/lymphoma (LL) cells to identify adhesion proteins involved in adherence between LL cells and marrow stromal cells. One mAb, 4C, and its subclones 4C.1 and 4C.2 inhibited adherence of L5178Y LL cells to MLT. a nontransformed murine marrow stromal cell line. These MoAbs are directed against CD45RA. Control anti-CD45 mAbs and isotype mAbs were non-inhibitory. Other anti-CD45 mAbs, M1/9.3, RA3-3A1/6.1 and RA3-2C2/1 do not compete with mAb 4C.1 for binding to the L5178Y cell surface, but mAb 4C.1 competes for binding of mAb RA3-2C2/1. Effects of mAb 4C on tyrosine-phosphatase activity of CD45 in L5178Y cells are minimal, suggesting direct involvement of CD45 as an adhesion protein.

Lymphocyte-fibroblast adhesion. A useful model for analysis of the interaction of the leucocyte integrin LFA-1 with ICAM-1

The adhesion of human T lymphoblasts to ICAM-1-expressing normal dermal fibroblasts has been assessed as a sensitive model system for the analysis of the interaction of the leucocyte integrin LFA-1 with its counter-receptor ICAM-1. Using this model system, the effects of factors known to regulate the activity of LFA-1 have been quantitated: temperature; concentration of divalent cations; and exposure to phorbol esters. We show here that under the appropriate assay conditions, this model system represents a useful and simple alternative to the detection of leucocyte binding to purified ICAM-1 and also has the additional advantage of permitting more sensitive quantification than is possible using the homotypic adhesion assay.