Phytohemagglutinin Response in Systemic Lupus Erythematosus: RECONSTITUTION EXPERIMENTS USING HIGHLY PURIFIED LYMPHOCYTE SUBPOPULATIONS AND MONOCYTES

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Abstract

The phytohemagglutinin (PHA) response of lymphocytes from untreated patients with systemic lupus erythematosus (SLE) was studied using highly purified subpopulations of cells involved in the transformation response: T lymphocytes, B lymphocytes, and monocytes. Cell transformation was quantitated using both tritiated thymidine ([3H]-TdR) incorporation into DNA and cytofluorographic determination of cellular DNA content. Dose-response curves using six concentrations of PHA and five concentrations of cells over 0-5 days revealed a decrease in [3H]TdR by stimulated lymphocytes from some SLE patients. This decrease in [3H]TdR was paralleled by a decreased percentage of cells in S, G2, and M phases of the cell cycle. However, abnormal response occurred entirely in those SLE patients who were hypocomplementemic. The etiology of the impaired response was further examined. Lymphocyte receptors for concanavalin A were studied using cytofluorography of lymphocytes stained with fluorescein-conjugated concanavalin A. The frequency distribution of concanavalin A receptors was similar in the normocomplementemic and hypocomplementemic lupus patients and in normals. The latex phagocytic activity of lupus macrophages was similar to normals when allogeneic normal plasma was used in the culture medium. Phagocytic activity became abnormal in the presence of SLE plasma. However, there was no difference in the [3H]TdR response or the percentage of cells in S, G2, and M phases when T lymphocytes from the hypocomplementemic patients were stimulated on either autologous or normal allogeneic monocyte monolayers. Likewise, normal lymphocytes incorporated similar amounts of [3H]TdR and had similar percentages of cells in S, G2, and M phases whether their T lymphocytes were stimulated on autologous or SLE monocyte monolayers. Highly purified subpopulations of B and T lymphocytes were obtained by density sedimentation or Fenwal Leuko-Pak passage of lymphocyte populations. The response to PHA by lymphocytes from the hypocomplementemic lupus patients could be seen to involve at least two abnormalities. One, in reference to normal lymphocytes, SLE T lymphocytes plus monocytes had an impaired response; two, SLE B lymphocytes plus SLE T lymphocytes plus SLE monocytes had an impaired response. Two patients in the hypocomplementemic group were treated with steroids. 5 days after steroid treatment was initiated, the percentage of cells in S, G2, and M phases and the [3H]TdR response of PHA-stimulated lymphocytes returned to normal. The normalization of the [3H]TdR response was explained both by a return of purified T cells plus monocytes, purified B cells plus monocytes, and whole lymphocyte populations to normal responsiveness. These studies suggest that a steroid-correctable defect exists in T and B lymphocytes in SLE.

Authors

Peter D. Utsinger, William J. Yount