Detection and spatial distribution of IL-2 receptors on mouse T-lymphocytes by immunogold-labeled ligands.
To identify the plasma membrane (PM) structures implicated in T-cell activation, we studied the distribution of interleukin-2 receptors (IL-2R) and the surface topography of lymphocytes by affinity labeling in electron microscopy (EM). In particular, we analyzed the distribution of the IL-2R alpha-chain on CTLL-2 cells (a murine cytotoxic T-cell lymphoma line). Some of our experiments were extended to the functionally and morphologically distinct cell line EL4 (a routine helper T-cell lymphoma line). As affinity ligands we used a rat monoclonal antibody (clone 7D4) reactive with the routine alpha-chain of IL-2R and recombinant mouse IL-2 (rIL-2). The distribution of IL-2R was visualized on the cell surface by ligands coupled to colloidal gold particles of different sizes. Unfixed cells were labeled with gold probes and attached to concanavalin A (ConA)-pretreated coverslips. Subsequently, the cells were prepared for EM. Examination of ultrathin sections and large surface replicas revealed a high degree of variability in cell morphology and in the density of the randomly distributed gold-labeled ligands among CTLL cells. According to their typical appearance, lymphocytes with strong receptor expression can be easily identified within the cell population. In contrast, the label on many mitogen-activated EL4 cells showed a cap-like polar distribution. The results suggest the existence of diverse distribution patterns of IL-2R on CTLL and EL4 cells. These differences are believed to reflect the different physiological roles played by T-cell subsets in the immune system.
Breitfeld
O
O
Heinrich-Pette-Institut für experimentelle Virologie und Immunologie an der Universitat Hamburg, Germany.
Kühlcke
K
K
Lother
H
H
Hohenberg
H
H
Mannweiler
K
K
Rutter
G
G
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D017979:Gold Colloid; D008024:Ligands; D051379:Mice; D051381:Rats; D015375:Receptors, Interleukin-2 / Q000378:metabolism*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology* / Q000648:ultrastructure; D014407:Tumor Cells, Cultured
D000911:Antibodies, Monoclonal; D017979:Gold Colloid; D008024:Ligands; D015375:Receptors, Interleukin-2