Lateral distribution of the ICAM‐1 molecule and its topological relationship (mutual proximity) to the heavy and light chains of class I HLA molecules, HLA‐DR and interleukin‐2 receptor α‐chain (IL‐2Rα) were studied in the plasma membrane of HUT‐102B2 T and JY B lymphoblastoid cell lines by the technique of flow cytometric energy transfer (FCET). Effects of adherency and treatments with recombinant interferon‐γ or tumor necrosis factor‐α on the relative expression level of ICAM‐1 to the above cell surface proteins were also investigated. While the cytokines did not significantly affect the ICAM‐1 level of either cell line, an increased ICAM‐1 expression was found on adherent JY cells. The ICAM‐1 expression varied significantly with the cell cycle and culture conditions, as well. The statistical analysis of the differences observed in the energy transfer efficiency histograms resulted in a possible model of lateral co‐distribution of these proteins in the plasma membrane. These two‐dimensional patterns proved to be different for T and B lymphoma lines. ICAM‐1 molecules showed a high degree of self‐ssociation on HUT‐102B2 (T) cells, while they were mainly expressed as monomers on the surface of JY (B) cells. Both cells showed a significant (ca. 30 %) difference between densities of the heavy and light chains of class I HLA antigen, suggesting a substantial amount of β2‐microglobulin free heavy chains on these cell lines. The class I HLA molecules also showed partial self‐association, but on both cell lines. The β2‐microglobulin and the heavy chain of the class I HLA showed strongly different proximities to the IL‐2Rα, HLA‐DR and ICAM‐1 molecules, indicating that their orientations relative to the other proteins are dissimilar. IL‐2Rα molecules of the HUT‐102B2 (T) cells are located mostly in the vicinity of the β2‐microglobulin. In contrast, the local density of HLA‐DR antigens is higher in the proximity of the heavy chain than in the vicinity of the β2‐microglobulin. The possible functional significance of these protein patterns is also discussed herein.
- Flow cytometric energy transfer
- HLA antigens
- Interleukin‐2 receptor
ASJC Scopus subject areas
- Immunology and Allergy