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Anti-CD2-induced T cell proliferation was analyzed in the peripheral blood samples of 31 primary and 8 secondary untreated Sjögren's syndrome patients. Anti-CD2-stimulated PBMC proliferation was very low in about one-third of primary Sjögren's syndrome samples, despite the number of CD2+ cells being similar in primary and secondary Sjögren's syndrome and normal PBMC samples. The depressed response to anti-CD2 was mainly found in anti-Ro+/La+ patients. Experiments on purified T cells demonstrated that a defect at the T cell level was responsible for the anti-CD2 unresponsiveness. Cell proliferation failure was associated with poor IL-2 and IL-2 receptor mRNA expression and, consequently, IL-2 and IL-2 receptor synthesis. Since defective anti-CD2-induced mitogenesis could be reversed by phorbol myristate acetate, but not calcium ionophore A23187, it is probably correlated with impaired protein kinase C activation. Comparison of anti-CD2-triggered PBMC proliferation in treated and untreated patients and a long-term study of nine patients showed that the defect is a stable characteristic in primary Sjögren's syndrome patients, but that it can be reversed by pharmacological immunosuppression.

Despite the fact that the percentage of circulating CD3-positive cells is similar in cord and adult blood, the proliferative response induced by anti-CD3 monoclonal antibody (mAb) was impaired in the majority of human cord peripheral blood mononuclear cell (PBMC) samples we tested. The cell proliferative defect was associated with low interleukin 2 (IL 2) gene expression and scant IL 2 production. However, interleukin 2 receptor was fully expressed at both the mRNA and protein levels. Such a finding is consistent with the observation that exogenous recombinant IL 2 is able to boost the anti-CD3-mediated response of cord PBMC. Furthermore, when anti-CD3 and phorbol myristate acetate (PMA) were added together, they exerted a very marked synergistic effect on both the proliferation of, and IL 2 production by, cord PBMC. The addition of allogeneic antigen presenting cells plus soluble anti-CD3 or Sepharose-coupled anti-CD3 mAb to the cord T cell cultures had no significant effect on proliferation, whereas both elicited good mitogenesis of adult T cells. Moreover, addition of exogenous recombinant interleukin 1 to anti-CD3-stimulated T cells failed to trigger any proliferation in either adult or cord samples. Since the combination of PMA and calcium ionophore A23187 is effective in triggering optimal proliferation of cord T cells, the defect would seem to be associated with a failure in transmembrane transduction of the activation signals provided by the anti-CD3 stimulus for the cord T cell.

The in vitro effect of a calf thymus extract, thymostimulin (TP--1), on the E-rosette-forming capacity and on the PHA blastogenic response of peripheral blood lymphocytes was evaluated in 20 patients with untreated Hodgkin's disease. The mean percentage of lymphocytes forming E rosettes increased in patients from 44.2% to 57.5% (P less than 0.005). The mean PHA stimulation index rose with all three concentrations tested, but returned to the normal range only with the highest PHA concentration (60 mu/ml). An increase in the immune parameters was greatest in those patients who presented with decreased E-rosetting cells of total lymphocyte counts or whose disease was Stage III or IV or of mixed cellular histology.

Because T-cell dysfunctions have been reported in patients with primary Sjögren's syndrome (SS), peripheral blood mononuclear cell (PBMC) proliferation obtained with anti-CD3 and anti-CD2 monoclonal antibodies was evaluated in these patients. Anti-CD3-induced mitogenesis, which varied widely among the patients, was lower in subjects with evidence of anti-SSA and anti-SSB antibodies than in controls. Moreover, the anti-CD2-induced response was depressed in about half the patients and the nonresponders were mainly those with anti-SSA and anti-SSB antibodies. Phorbol myristate acetate, a protein kinase C activator, used alone or added to anti-CD3, induced greater proliferation in patients than in control PBMC. In contrast, exogenous recombinant interleukin 2 (rIL-2) did not significantly enhance the anti-CD2-induced response of patients' PBMC, as it did in normal PBMC. Peripheral blood and parotid T cells from a patient with well-defined primary SS and parotid enlargement also responded poorly to anti-CD2 stimulation. Exogenous rIL-2 restored T-cell proliferation only in the salivary gland cultures of this patient. The present findings suggest that there is a T-cell activation defect in subjects with primary SS, particularly in those with circulating anti-SSA and anti-SSB antibodies. In addition, the difference in the response to IL-2 of peripheral blood and parotid-infiltrating T cells would seem to indicate that T-cell subsets are differently distributed in the blood and inflammation site.

The in vivo effect of a calf thymus extract (thymostimulin, TS) on the E-rosetting capacity, PHA blastogenic response, serum migration inhibitory activity (LIF) and skin reactivity to recall antigens was evaluated in 19 untreated patients with Hodgkin's disease. In patients the mean percentage of peripheral blood lymphocytes forming E-rosettes increased from 47 to 55.7% (P less than or equal to 0.001; normal: 58.9). The mean PHA stimulation index rose with all three concentrations tested but did not reach normal values. Serum LIF was positive in only one patient prior to treatment with a mean LIF for all patients of 0.75 (P less than or equal to 0.005). Skin tests were positive in ten patients (52.6%) prior to therapy and 18 patients following therapy (94.7%; P less than or equal to 0.05). Thymostimulin, in vivo, appears to return immunologic competency to a population of untreated patients with Hodgkin's disease.

The capacity of peripheral blood lymphocytes from fifteen patients with untreated Hodgkin's disease to form E-rosettes with sheep erytrocytes and to respond to PHA stimulation was found to be impaired in 47% of patients. When peripheral blood lymphocytes were incubated overnight in culture medium containing 20% fetal calf serum, E-RFC levels and the capacity to respond to PHA returned to normal. These functions were resuppressed by additional incubation with Hodgkin's disease serum but not from normal serum. The Hodgkin's disease serum inhibited normal peripheral blood lymphocytes to form E-rosettes and to respond to PHA.

A study was carried out on cord blood T cell activation via the CD2-mediated pathway. Despite similar percentages of circulating CD3+ and CD2+ cells in adult and cord blood, the proliferation of cord PBMC to the anti-CD3 mAb and cord T cells to anti-CD2 mAb were defective. The T cell CD3-surface structure was normally able to control CD2-mediated activation, as its modulation by a non-mitogenic anti-CD3 mAb blocked cord PBMC proliferation induced by anti-CD2 mAb. CD2-stimulated cord T cells did not proliferate and did not produce a significant amount of IL-2 in culture, although they expressed the IL-2R. This observation was confirmed by the optimal proliferation of CD2-induced cord T cells when rIL-2 was added. Despite the alternative T cell activation pathway is monocyte-independent in adults, the defective cord T cell activation via the CD2 molecule could also be bypassed by the addition of PMA, small amounts of either autologous or allogeneic adult and cord AC or simply rIL-1 alone. Our findings provide evidence for an intrinsic functional defect in cord CD2-mediated T cell activation, which is linked to an impaired increase of free cytoplasmic calcium, as confirmed by the effectiveness of calcium ionophore A23187 in restoring a good CD2-induced cord T cell proliferation and by measurement of cellular calcium uptake after activation via the CD2 molecule. The characteristics of cord T cells revealed by this study recall the thymocyte functional pattern and may represent functional expression of the previously described phenotypic immaturity of cord T cells.