Ruthann Kibler

Prolactin receptors on human lymphocytes and their modulation by cyclosporine

Prolactin receptors have been identified for the first time on human peripheral blood lymphocytes. These receptors are present on T- and B-cells as well as monocytes. The specific binding of [125I]prolactin to these cells can be selectively enhanced at certain concentrations and blocked by higher concentrations of cyclosporine , a known immunosuppressive agent which inhibits the mitogenesis of T-cells. Prolactin also induces ornithine decarboxylase, a key growth regulatory enzyme, in lymphocytes. Therefore, we suggest that the lymphocyte prolactin receptor may be involved in regulating lymphocyte function, and that one of the actions of cyclosporine is to block this rather ubiquitously occurring receptor.

Immune function in chronic active Epstein-Barr virus infection

The spectrum of illness attributed to Epstein-Barr virus (EBV) includes patients with symptoms persisting for more than 1 year without any other obvious underlying disease. High titers of antibodies to EBV, either IgG anti-viral capsid antigen or anti-early antigen, can be demonstrated. In this study, 13 patients diagnosed as having chronic active EBV infection were examined to determine aspects of their immunologic status. Morphological examination and fluorescent antibody analysis revealed no abnormalities in the phenotypes of peripheral blood white cells present in these patients. Compared to those from healthy control individuals, mononuclear cells from the patients showed a markedly depressed ability to produce both interleukin-2 and interferon after stimulation with mitogen and a phorbol ester. Studies of natural killer (NK) cell activity revealed that unfractionated mononuclear cells from patients with chronic active EBV infection were significantly lower in killing activity compared to the control group. Fractionation procedures to enrich for large granular lymphocytes resulted in an increase in NK activity for all individuals, but killing activity still remained slightly lower in the patients than in the control group. The dysfunctions which were found in patients with chronic active EBV infection may reflect a primary defect in natural immune functions of the patients predisposing them to a chronic or intermittent clinical disease rather than a self-limiting illness. Alternatively, the abnormalities detected in these experiments may be a result of the viral infection itself.

Prolactin stimulation of ornithine decarboxylase and mitogenesis in Nb2 node lymphoma cells: The role of protein kinase C and calcium mobilization

The tumor promotor 12-O-tetradecanoylphorbol-13-acetate (TPA) in combination with calcium ionophores has been shown to bypass the requisite antigen- or lectin-induced signal for lymphocyte mitogenesis. This suggests that protein kinase C activation and calcium mobilization may be early events required for lymphocyte proliferation. Therefore, the relationship(s) of protein kinase C activation and calcium mobilization to ornithine decarboxylase induction and cellular proliferation were examined in a rat node lymphoma cell line (Nb2) which is dependent upon prolactin (PRL) for mitogenesis. TPA enhanced PRL-stimulated Nb2 node lymphoma cell ornithine decarboxylase induction and [3H]thymidine incorporation. Addition of a calcium ionophore (A23187) to cultures containing TPA plus PRL increased ornithine decarboxylase above PRL alone or PRL plus TPA but inhibited proliferation compared to the PRL plus TPA regimen. Exposure of cells to TPA or TPA plus A23187 increased [3H]thymidine incorporation in a similar manner to that demonstrated for low-dose PRL. However, optimal concentrations were only 20-25% as effective as mitogens as was optimal PRL. Protein kinase C and calmodulin antagonists inhibited PRL-stimulated ornithine decarboxylase induction and proliferation. Ca2+ chelation or cation channel antagonism inhibited both PRL-stimulated responses. The cyclic AMP analogue, 8Br-cAMP, inhibited PRL-stimulated ornithine decarboxylase activity as well as cellular proliferation processes assessed by [3H]thymidine incorporation. Finally, tumor-promoting phorbol esters inhibited 125I-rPRL binding. These data strongly suggest that protein kinase C activation and calcium mobilization are requisite events for PRL-stimulated ornithine decarboxylase induction and cellular proliferation in Nb2 node lymphoma cells. An additional component that is linked to alterations in K+ channeling is also implicated. These data support a role for protein kinase C in PRL-coupled mitogenesis. However, other critical Ca2+ and/or ion-induced events are also required.

999 HUMAN CORD BLOOD: LYMPHOCYTE SUBPOPULATIONS AND LYMPHOKINE PRODUCTION

As part of a study of respiratory health and immunity of children, 61 cord blood specimens were separated into a mononuclear cell population (>70% lymphocytes). Total T, helper T, supressor/cytotoxic (sup/cy) T and natural killer (NK) cells were determined by rosette (ER) and immunofluorescent methods (OKT3, OKT4, OKT8, Leu 11 respectively). B cells were detected by the presence of membrane immunoglobulin. Interleukin-2 .(IL-2) and interferon (IFN) production were measured in supernatant fluids of Con A and phorbol ester stimulated cells. IL-2 units were determined by probit analysis, and IFN titers were based on a 50% reduction in virus cytopathic effect (log3, dilution). NK assays were performed at 5 effector to target cell ratios on K562 cells, and lytic units/106 lymphocytes (LU) were calculated. The mean % ± SD for these results are compared to adult values (N=38 to 74).T sup/cy cells, IFN titers and NK activity were lower while the T4/8 ratio and IL-2 production were increased for cord blood. These findings may relate to the increased susceptibility of neonates to infection. (Supported by NHLBI-SCOR Grant# HL1436-1351 and The Southwestern Clinic and Research Institute).