Analysis of T cell stimulation by superantigen plus major histocompatibility complex class II molecules or by CD3 monoclonal antibody: costimulation by purified adhesion ligands VCAM-1, ICAM-1, but not ELAM-1.

Abstract

SummaryMany ligands of adhesion molecules mediate costimulation of T cell activation. The generality of this emerging concept is best determined by using model systems which exploit physiologically relevant ligands. We developed such an "antigen-specific" model system for stimulation of resting CD4 + human T cells using the following purified ligands: (a) major histocompatibility complex class II plus the superantigen Staphylococcus enterotoxin A, to engage the T cell receptor (TCR); (b) adhesion proteins vascular cell adhesion molecule 1 (VCAM-1), intercellular adhesion molecule 1 (ICAM-1), and endothelial leukocyte adhesion molecule 1 (ELAM-1), to provide potential cell surface costimulatory signals; and (c) recombinant interleukin 13 (rlL-13)/rlL-6 as costimulatory cytokines. In this biochemically defined system, we find that resting CD4 + T cells require costimulation in order to respond to TCR engagement. This costimulation can be provided by VCAM-1 or ICAM-1; however adhesion alone is not sufficient since ELAM-1 mediates adhesion but not costimulation. The cytokines IL-13 and IL-6 by themselves cannot mediate costimulation, but augment the adhesion ligand-mediated costimulation. Direct comparison with the model of TCR/CD3 engagement by CD3 monodonal antibody demonstrated comparable costimulatory requirements in both systems, thereby authenticating the commonly used CD3 model. The costimulation mediated by the activation-dependent interaction of the VLA-4 and LFA-1 integrins with their respective ligands VCAM-1 and ICAM-1 leads to increased IL-2Rot (CD25) expression and proliferation in both CD45RA + CD4 + and CD45RO + CD4 + T cells. The integrins also regulate the secretion of IL-2, IL-4, and granulocyte/macrophage colony-stimulating factor. In contrast the activation-independent adhesion of CD4 + T cell to ELAM-1 molecules does not lead to T cell stimulation as measured by proliferation, IL-2Rot expression, or cytokine release. These findings imply that adhesion per se is not sufficient for costimulation, but rather that the costimulation conferred by the VLA-4/VCAM-1 and LFA-1/ICAM-1 interactions reflects specialized accessory functions of these integrin pathways. The new finding that VLA-4/VCAM-1 mediates costimulation adds significance to observations that VCAM-1 is expressed on a unique set of potential antigen-presenting cells in vivo.T cell stimulation mediated by antigen requires specific engagement of the TCR/CD3 complex with antigenic peptides presented by MHC molecules. In general these interactions alone are not sufficient to stimulate T cells, but require additional costimulatory signals provided by the APC to achieve T cell activation and differentiation (see for review references 1 and 2). mAb blocking studies in APC-dependent T cell proliferation models have been instrumental in

Crosslinking of the T cell-specific accessory molecules CD7 and CD28 modulates T cell adhesion.

“…1 B), A23187, CD7, and CD28 crosslinking also increase adhesion to the VLA-4 ligand VCAM-1 (Fig. I A), extending our earlier findings on VCAM-1 adhesion using PMA activation (21,23). These results suggest that these activation signals act coordinately on multiple T cell integrins, enabling T cells to adhere to a variety of cell surface and ECM ligands, mAb blocking studies demonstrated that adhesion to these ligands after activation occurs via the expected integrin receptors (data not shown).…”

“…The ICAM-1 was purified by affinity chromatography from the ReedSternberg cell line L428 as previously described (19). Recombinant, soluble VCAM-1 was isolated from the culture supernatants of Chinese hamster ovary cells expressing a truncated form of the fulllength VCAM-1 cDNA as previously described (20,21 Adhesion Assays. Adhesion assays were performed as described (4).…”

Human Vascular Endothelial Cells Stimulate Memory But Not Naive CD8+ T Cells to Differentiate into CTL Retaining an Early Activation Phenotype

“…HUVEC do not express the ligands for either CD28 (B7.1 and B7.2; Ref. 10) or CD137, the human equivalent for mouse 4-1BB (ILA; T. J. Dengler, unpublished observation), and the T cell costimulatory potential of VCAM-1 and E-selectin are thought to be of minor importance (20,35). However, exogenous costimulatory enhancement with a comitogenic anti-CD28 mAb was also without effect on CTL generation.…”

Arterial and venular endothelial cell costimulation of cytokine secretion by human T cell clones

“…6 and 7). These molecules have been implicated in regulating costimulation directly [49] and indirectly [16,50] in studies using purified molecules bound to plastic. ICAM-1 and VCAM-1 are well-defined mediators of adhesion [15] and, together with other EC molecules [10], they may function principally in strengthening EC-lymphocyte interactions, thereby encouraging lymphocyte binding and recruitment from the bloodstream [51].…”