Mitogenic effect of PMA + IL 2 on subpopulations of corticoresistant thymocytes.

The proliferative response of subpopulations of corticoresistant thymocytes (CRT) to phorbol-12-myristate-13-acetate (PMA) + interleukin 2 (IL 2) was investigated. Thymocyte subpopulations were selected by the indirect "panning" technique, and their purity was checked by cytofluorometry. Microcultures were set up with an optimal concentration of PMA, EL4 supernatant, or pure IL 2 obtained by recombinant DNA technology (r-IL 2) in the presence or in the absence of accessory splenic adherent cells (SAC). Under these conditions, only the Lyt-2+ CRT proliferated, and this response was IL 2-dose-dependent and was increased by accessory cells. When the calcium ionophore A23187 was added to the cultures, the proliferation of L3T4+ CRT was greatly increased. These results were confirmed by cultures at limiting dilution of positively selected Lyt-2+ and L3T4+ subpopulations of CRT at optimal concentrations of PMA, r-IL 2, A23187, and accessory cells. These results are consistent with the idea that two signals are necessary to activate L3T4+ CRT, whereas only IL 2 is necessary for PMA-induced proliferation of Lyt-2+ CRT. Finally, unlike the case of lectin-induced proliferation of Lyt-2+ and L3T4+ CRT, the presence of accessory cells or cell-cell contact is important for optimal response to PMA + IL 2.

5'-nucleotidase activity of murine T-cell subpopulations separated according to their Lyt2 and L3T4 phenotypes.

Murine T lymphocytes were separated by "panning" into four subpopulations, according to their Lyt2 and L3T4 phenotypes: Lyt2+L3T4+, Lyt2-L3T4-, Lyt2+L3T4-, and Lyt2-L3T4+. The activity of ecto-5'-nucleotidase in each subpopulation was measured. 5'-Nucleotidase activity was undetectable in Lyt2+L3T4+ cortical cells but was expressed in medullary Lyt2-L3T4+ and Lyt2+L3T4- T lymphocytes. The small cortical subpopulation of thymocyte precursors with the Lyt2-L3T4- phenotype expressed levels of 5'-nucleotidase comparable to the levels of medullary, mature lymphocytes. These results suggest that the use of ecto-5'-nucleotidase as a marker of the degree of T-cell maturation is questionable.

[Neonatal jaundice due to anti-D allo-immunization with negative direct Coombs' test]. / Ictere neonatal par allo-immunisation anti-D avec test de Coombs direct negatif

The case is reported of a newborn with jaundice due to anti-D Rh iso-immunization, with a negative Coombs' test. The finding of a positive red cell auto-agglutination test, the red cells being treated with bromelin and incubated in their own serum, suggests an immune phenomenon. Free antibody with anti-D specificity reacting with bromelin treated R.B.C.'s was found in the sera of the mother and infant.