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The changes occurring in surface morphology during the transformation of normal peripheral blood lymphocytes by phytohaemagglutinin (PHA) are described and the surface ultrastructure of the PHA-induced blasts is compared with that of pokeweed mitogen (PWM)-and rabbit anti-beta2-microglobulin antiserum-induced blasts. Both mitogen-specific and non-specific changes were observed and their possible relationship to the activation of lymphocyte subpopulations is discussed. Similar surface characteristics found in various tissue lymphoid cells are also described.

The properties have been studied of a haemic cell line established from a patient with longstanding non-Hodgkin's lymphoma after transformation to acute leukaemia. The cells are EBNA, Fc, C3 and SmIg and Ia-like antigen negative. The continuous in vitro proliferation and karyotype abnormalities suggest malignancy. The cells contain only the lymphoid type of alkaline phosphatase and a high level of terminal deoxynucleotidyl transferase and as they formed E-rosettes during the first year in culture they may be of T-cell lineage. Since the patients' leukaemic cells have not been studied it is impossible to know whether the cultured cells represent an in vitro proliferation of the patient's malignant cells or an outgrowth of a subpopulation of cells. In the cytoplasm of many cells inclusion bodies containing virus-like particles, similar to those observed in fresh human leukaemia cells, were often seen. As this new virus is biologically active, infection of the cells by virus may explain their continuous proliferation in vitro.

The distribution of light and heavy immunoglobulin chains in chronic lymphocytic leukemia (CLL) cells has been investigated at the ultrastructural level using an immunoperoxidase technique. Light chains were localized in the lumens of the perinuclear space and rough endoplasmic reticulum, while staining for heavy chains was weak or negative and generally confined to the membranes of the rough endoplasmic reticulum. This pattern is consistent with immunoglobulin biosynthetic studies on CLL cells in which light chains are synthesized in excess over heavy chains and secreted as the exclusive immunoglobulin product. The pokeweed mitogen stimulation of two populations of CLL cells for 6 days resulted in a balanced synthesis and secretion of light and heavy chains that was reflected in concomitant change in light and heavy chain distribution and intensity of staining using the immunoperoxidase technique.