Is the adherent, non-specific 'suppressor' cell from rodent spleens an in vitro artefact?

Mitomycin C-treated cells from the spleens of mice pre-treated with BCG, Corynebacterium parvum, cyclophosphamide or methylcellulose will inhibit the mitogen responses of normal cells in vitro, but extended dose-response studies have shown that such cell populations will also enhance the response if added in very small numbers. The number of cells giving peak enhancement is proportional to the percentage of the spleen cells which are adherent at 72 hr. Such late-adhering cells are not removed by conventional adherence column techniques. The concept of the adherent suppressor T cell is discussed in the light of these findings.