Signaling through the LFA‐1 leucocyte integrin actively regulates intercellular adhesion and tumor necrosis factor‐α production in natural killer cells

Abstract

The LFA-1 leucocyte integrin is known to participate in natural killer (NK) cytolytic activity, mediating effector target interactions. The possibility that LFA-1 may also play an active regulatory role in NK cells has been explored. To this end, we have employed a monoclonal antibody (HP1N) raised against recombinant interleukin-2 (rIL-2)-activated NK cells, which recognizes the alpha chain of the LFA-1 heterodimer (CD11a). In contrast to other anti-CD11a mAb the HP1N and its F(ab')2 fragment did not affect NK cell-mediated cytotoxicity and triggered a strong homotypic adhesion of NK cells and other LFA-1+ cells. Cellular aggregation was inhibited by anti-CD18 mAb, anti-ICAM-1 mAb, and other anti-CD11a mAb. Remarkably, the HP1N mAb was also shown to induce tumor necrosis factor-alpha (TNF-alpha) production from NK cells upon costimulation with anti-CD16 mAb. Such an effect appeared to be independent from homotypic adhesion since it took place in Mg(2+)-free medium, where NK cell aggregation was inhibited. Moreover, incubation with the HP1N mAb triggered a Ca2+ influx into the cytosol; this effect was clearly observed upon cross-linking of cell bound HP1N and was also substantiated with other anti LFA-1 (CD11a and CD18) mAb. Taken together these results indicate that the LFA-1 molecule is capable of transducing signals in NK cells, which regulate the intercellular interaction with its ligand, and enhance the activation via Fc gamma receptor type III.

Interactions Between Natural Killer Cells, Cortisol and Prolactin in Malaria During Pregnancy

“…It is well known that β2 integrins expressed on the surface of NK cells recognize intracellular adhesion molecule-1 (ICAM-1) on target cells. 15,16 However, this may be one of several receptor ligand pairs that are involved in the recognition process. Another adhesion ligand pair, CD2 on NK cells, recognizes LFA-3 on target cells.…”

“…Unlike many viral proteins that downregulate class I molecules, CMV US2 and CMV US11 are specific to HLA-A and -B alleles, but do not affect HLA-C molecules showing allelic specificity. 35 CMV UL40 has been interesting because of the homology between the signal sequence (amino acids 3-11) of most HLA-C alleles and the UL40 peptide (amino acids [15][16][17][18][19][20][21][22][23]. Two independent laboratories have recently found UL40 sequence homology to HLA-E binding peptides.…”

Thrombopenic purpura induced by a monoclonal antibody directed to a 35-kilodalton surface protein (p35) expressed on murine platelets and endothelial cells

“…For hybridoma production [23], spleen cells from an immunized rat were fused with NSO myeloma cells (kindly provided by Dr. Milstein, Cambridge, United Kingdom) at a ratio of 5:1 and distributed in 96-well plates (Costar, Cambridge, MA, USA). Screening of mAb reaction with endothelial cell-surface antigens was performed by indirect immunofluorescence and flow cytometry (FACScan; Becton-Dickinson, San Jose, CA, USA).…”

“…After washing twice in cold PBS, cells were lysed in 1 mL of lysis buffer containing 1% Triton X-100 and 1 mM PMSF. Equivalent amounts of lysates were used to immunoprecipitate with the mAb, as previously described [23]. Immunoprecipitates were analyzed by 10% SDS-PAGE and transferred onto a PVDF membrane (Immobilon-P; Millipore, Bedford, MA, USA).…”

“…A panel of mAbs was obtained after immunization with a mouse-derived endothelial cell line (PY4.1) [22] by fusing splenocytes from immunized rats with mouse myeloma cells, as previously described [23]. The hybridoma EOL5F5 (rat IgG2b) (Fig.…”