Normal human CD3+ T cells express all types of dopamine receptors (DRS) – D1R‐D5R on their cell surface, and the level of D1R, D5R and D4R are higher in activated T cells than in resting T cells. (a–e; Upper Figs) Expression of D1R–D5R on resting normal human CD3+ T cells. (f–j; Lower Figs) Expression of D1R–D5R on CD3/CD28‐activated normal human CD3+ T cells. The colored graphs show the levels of immunofluorescence staining, first with rabbit‐anti‐human antibodies selective to each DR type, and then with a secondary‐FITC‐conjugated goat anti‐rabbit antibody. The control gray fluorescence profiles in each graph represent the control non‐specific staining, first with rabbit isotype control, and then with the same secondary antibody. The results are of one representative experiment, of two performed on T cells of different healthy human individuals. In both experiments the same pattern of results was observed, but the actual numbers/expression levels were different. This observation is in line with the findings of Kustrimovic et al.,7 that human T cells express all DR types, but that there is a remarkable variability between different people with regard to the exact level of each DR type expressed on the cell surface of their T cells.