A pen smear technique for assays of rosette-forming lymphocytes

A simple technique is described for the preparation of permanent stained smears of human E-rosette lymphocytes. Smears of the cells suspended in foetal calf serum were drawn as thin strips on slides with a pen nib. Such smears, after Romanowsky staining, and incorporating latex-particles phagocytosis as a marker for non-lymphoid cells, show excellent rosette preservation and permit easy distinction and counting of rosetting lymphocytes, non-rosetting lymphocytes, monocytes and granulocytes. The percentages of rosette-forming lymphocytes estimated on such smears correspond closely to those obtained from counts made on viable cell suspensions.