The tumor progression-associated human melanoma antigen P3.58 mediates monocyte-lymphocyte interactions in vitro

Differential expression of two ICAM-1 epitopes and LFA-1 chains in B-cell non-Hodgkin's lymphomas

B-cell non-Hodgkin's lymphomas (B-NHL) and B-cell areas of reactive lymphadenopathies were investigated immunohistochemically for expression of two distinct ICAM-1 epitopes, Me14/D12 and P3-58, and the LFA-1 alpha and beta chains. Partial or total loss of expression of one or both epitope(s) and/or chain(s) was evident in all B-NHL in function of increasing Working Formulation (WF) malignancy grade, with most defects in the high-grade tumors, namely the lowest detectability of the ICAM-1 Me14/D12 and LFA-1 alpha chain, the lowest co-expression of ICAM-1 epitopes and LFA-1 chains, and the most frequent simultaneous loss. The ICAM-1 and LFA-1 profiles overlapped within the low- and intermediate-grades, whereas striking differences between the high-grade subtypes were detected. Specifically, Burkitt's and lymphoblastic tumors always lost both epitopes and both chains. Large cell, immunoblastic tumors occasionally did so, and also showed either uncoordinated expression or co-expression of these constituents. It is suggested that expression defects of this type may help differentiate malignant from benign lymphoproliferations, and also be involved in the progression of B-NHL, since most are observed in high-grade tumors, whose ICAM-1 and LFA-1 profiles indicate that their subtypes are the expression of distinct normal B-cell differentiation stages.

Generation of recombinant, carbohydrate-free intercellular adhesion molecule-1 (ICAM-1) and ICAM-1 fragments in Escherichia coli and mapping of epitopes recognized by anti-ICAM-1 monoclonal antibodies

Intercellular adhesion molecule-1 (ICAM-1) has been shown to interact with the integrin leukocyte function associated antigen-1 (LFA-1) in a variety of cell-cell adhesion phenomena. Furthermore, it serves as a receptor for the majority of the Rhinoviruses and for Plasmodium falciparum-infected human erythrocytes. We generated recombinant, carbohydrate-free ICAM-1 and several ICAM-1 fragments by expression in Escherichia coli using the fusion protein expression system pUEX1-3. In Western blot and dot blot analyses we tested mAbs (7F7, 8B9, P3.58-BA3, -BA11, -BA14, -BA19, -BA21, -BA23, -BA24, -BA26, CL203.4 and 84H10) and a polyclonal antiserum directed against native ICAM-1 for their reactivity with these constructs. We were able to localize the binding site for the mAbs P3.58-BA3, -BA11, -BA14, -BA19, -BA21, -BA23, -BA24 and -BA26 at domain 5, whereas the mAbs 7F7, 8B9, CL203.4 and 84H10 did not recognize the recombinant, carbohydrate-free ICAM-1. Our findings suggest the presence of an immunodominant epitope on domain 5 of ICAM-1.

Roles of adhesion molecules in T-cell recognition: fundamental similarities between four integrins on resting human T cells (LFA-1, VLA-4, VLA-5, VLA-6) in expression, binding, and costimulation

This review summarizes our recent work on expression and function of 4 integrins on resting human CD4+ T cells. Three themes are highlighted: multiplicity of molecular pathways of adhesion, regulation of adhesion, and costimulation by adhesion molecules. Four distinct receptor/ligand interactions have been elucidated: LFA-1/ICAM-1, VLA-5/fibronection, VLA-4/fibronectin, and VLA-6/laminin. Our studies indicate fundamental similarities in function and regulation of these four receptor/ligand interactions: 1) acute activation of the T cell (by CD3/TCR crosslinking or by PMA) induces rapid but transient integrin binding function; and 2) higher expression of each integrin on memory T cells compared to naive T cells results in greater binding of memory cells to each ligand. The identification of T-cell integrins (VLA-4, VLA-5, VLA-6) which interact with ECM components directs attention to the potential importance of T-cell interactions with ECM components which either may be immobilized in ECM or which may act as molecular bridges between cells. The existence of multiple adhesion pathways, of multiple ligands for a single receptor (such as LFA-1/ICAM-1 and LFA-1/ICAM-2), multiple receptors for a single ligand (such as VLA-4/FN and VLA-5/FN), and regulation of ligand expression (ICAM-1) provides opportunities for co-operativity, rebundancy and diversity which the T cell utilizes to exquisitely regulate its adhesive interactions. The thesis that adhesion molecules can be multifunctional receptors that also influence signalling is demonstrated by our findings that each of these integrin receptor/ligand interactions is capable of providing a potent costimulatory signal to CD3-mediated T-cell activation. The importance of interactions of T-cell integrins with their cell surface and ECM ligands is discussed with respect to T-cell migration, differentiation and recognition. Analysis of the precise mechanisms by which T cells regulate and exploit these multiple receptor/ligand interactions and the resulting functional consequences of those interactions will be exciting areas of future research.