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Recent studies have been carried out to delineate further the role of the Rb1 gene in B-cell chronic lymphocytic leukaemia (B-CLL). The suggested role of the Rb1 gene in this disease was based on cytogenetic data. CLL patients (40 in toto) were examined using cytogenetic and molecular biological methods. R-banding analysis of metaphase chromosomes revealed aberrations in only seven cases containing either the Rb1 gene or a chromosome 13 monosomy. No evident differences were found by RT-PCR analysis of Rb1 gene expression. The amounts of the RT-PCR products obtained appeared to be approximately equal in all cases, and was independent of the clinical stage, immunophenotypes and LPS or TPA stimulation.

The in vitro production and secretion of the immunoglobulins IgM, IgG, Kappa and lambda light chains by peripheral blood lymphocytes from chronic lymphocytic leukaemia patients was examined. The ELISA system was employed to quantitate the immunoglobulins secreted in the culture supernatants. Lipopolysaccharide and phorbol esters with CA++ ionophore were used as lymphocyte stimulators. The maturation of cultured lymphocytes was demonstrated by synthesis of cytoplasmic immunoglobulins and Ig secretions typical for plasma cells. In one case an isotype switch C mu for C gamma was observed.

Physico-chemical properties and RNA synthesis in the rat liver and human lymphocytes have been compared in a nuclear system in vitro. Human lymphocytes were isolated from blood of healthy donors and of chronic lymphocytic leukaemia patients. The isolated nuclei served as the source of polymerase and template DNA. 3H-CTP was incorporated into the acid insoluble fraction linearly for 60 min. The nuclei of lymphocytes contained small amounts of RNA and protein, and the isolation procedure was complicated. Rat liver nuclei seem to be less prone to clumping at high pH values and may incorporate much more 3H-CTP. The nuclear synthesis was compared with incorporation of 3H-rU and 32P-orthophosphate into nuclear RNA of intact lymphocytes. Normal cells easily incorporated 32-P, and in contrast leukaemic cells incorporated 3H-rU to a greater extent.

In vitro transcription of stimulated T lymphocyte nuclei was studied using a previously described method for evaluating the accumulation of double labelled transcription products. Whereas RNA elongation was inhibited during the G0 and S phases of the cell cycle, the synthesis of short-living products (probably products of abortive initiation) still proceed in vitro. Release of the elongation block with concommitant decrease of short-product synthesis was observed during the G1 phase.

Peripheral blood lymphocytes from five patients with B-derived chronic lymphocytic leukaemia were stimulated by Staphylococcus aureus strain Cowan together with T cell mitogen phytohaemagglutinin in 5-9 days suspension cultures. The responses of B lymphocytes were studied on a T cell depleted subpopulation, obtained from harvested lymphocyte cultures using the sheep red blood cell rosette technique. Proliferation tests were performed using a 3H-TdR blast cell index. The maturation process of B-lymphocytes was examined with cytoplasmic Ig studied by FITC-conjugated antisera. Results analysed indicate various degrees of maturation of B cells in different patients.