Studies of lymphocyte proliferation in hairy cell leukaemia: activity in mixed lymphocyte reaction and responses to mitogens

Clonal T-lymphocytes from untreated hairy-cell leukaemia patients enhance the growth of BFU-E

The anaemia in hairy cell leukaemia (HCL) has been suggested to be mediated in part by T lymphocytes. Consequently, we have investigated the role of T lymphocytes in this disease by cloning pre-treatment HCL T lymphocytes and testing their influence on the in vitro growth of BFU-E from autologous post-treatment and normal donors T-lymphocyte depleted peripheral blood mononuclear cells (PBMNC-T). Altogether, 24 CD4+/CD8- and 17 CD4-/CD8+ T-lymphocyte clones from 3 different HCL patients were tested. All were found to enhance the growth of BFU-E, the degree of enhancement being independent of the length of IFN treatment at the time of the post-treatment sampling. Likewise, no difference in the extent of enhancement was seen between CD4+/CD8- and CD4-/CD8+ clones, or whether the clones were tested for modulation of BFU-E from PBMNC-T of autologous or allogeneic origin. Finally, no differences could be observed between different patients in the extent of clonal enhancement. These findings, which are in line with our previous ones in normal donors, indicate that the T-lymphocyte function with regard to regulation of the erythropoiesis is normal in HCL, arguing against a T-lymphocyte mediated suppression of the erythropoiesis in HCL.

Natural-killer-stimulatory effect of combined low-dose interleukin-2 and interferon beta in hairy-cell leukemia patients

The association of low doses of interleukin-2 (IL-2; 5 IU/ml) and interferon beta (IFN beta; 10 IU/ml) induced an additive or synergic stimulatory effect on natural killer (NK) activity (32%) in peripheral blood samples from hairy-cell leukemia patients, both those with active disease and those in remission. The synergic NK stimulatory effect was more commonly found in samples from patients with active disease, while the additive effect was more frequent in the patients in remission. The IL-2/IFN beta combination provoked a nonadditive nonsynergic NK-stimulatory effect in a further 19.8% samples. The targets of the IL-2/IFN beta combination were typical NK cells, as shown by the fact that there was increased cytotoxicity (synergic, additive or nonadditive nonsynergic) against the K562, but not the Daudi cell line in peripheral blood mononuclear cell samples treated with the combination of the two cytokines. When CD16+/CD56+ or CD57+/CD16+/CD56+ cells were removed, the NK-stimulatory effect was lost. The fact that the NK-cell-enhancing activity of the IL-2/IFN beta combination was reduced when Percoll fractions 2 and 3 were used, but still persisted in 66% of tests, may have been due to cytotoxicity being higher in the untreated fractions 2 and 3 than in the untreated unfractionated samples. One of the factors responsible for the NK-stimulatory effect appears to be the capacity of the IL-2/IFN beta combination to trigger an increase in IFN gamma synthesis. If similar experiments give like results in samples from patients suffering from other B-cell lymphoproliferative, or HIV-associated disorders, all of which are characterized by a deficiency in NK activity, it should be possible to use low-dose IL-2/IFN beta to treat these disorders and, perhaps, residual neoplastic disease without exposing the patient to undue toxicity. Further, by testing other combinations one should be able to identify the lowest IL-2 and IFN beta doses that would effectively boost the additive or synergic effect in a greater number of cases.

Mechanism of the immunoregulatory effect of cloned T cells on proliferation in mixed lymphocyte responses

The mechanism of the suppression of the mixed lymphocyte response (MLR) by T cell clones derived from the murine AMLR was studied in a system employing .45 microns membrane chambers to isolate the cellular reactants. The clones effectively suppressed MLR regardless of the MHC haplotype of the reactants in the absence of direct cellular contact, via a soluble factor able to pass through this membrane. Utilizing specific neutralizing antibodies, this factor was shown to be principally TNF alpha, with a contributing effect of gamma interferon. Production of TNF alpha by the cloned T cells was confirmed by direct assay of clone culture supernatants.

Reduced production of tumor necrosis factor by mononuclear cells in hairy cell leukemia patients and improvement following interferon therapy

In 16 patients with hairy cell leukemia (HCL) there was a marked reduction in the production of cytotoxins (CTXs) by peripheral blood mononuclear leukocytes in response to stimulation in vitro by phytohemagglutinin (PHA), 4 beta-phorbol-12-myristate-13-acetate (PMA), or Sendai virus. CTX yields of 23.5 +/- 21.5 U/ml, 15 +/- 18 U/ml, and 12.1 +/- 12.1 U/ml were obtained in response to PHA, PMA, and Sendai virus, respectively, as compared with corresponding yields of 207.3 +/- 93.1, 154 +/- 37.4, and 205.2 +/- 62.4 in healthy controls. The extent of reduced production of CTXs appeared to be correlated with the severity of the disease. Systemic interferon (IFN) administered to four patients caused CTX production to improve in response to PHA (147.5 +/- 55.1 U/ml compared with pretreatment values of 14.1 +/- 6 U/ml, P less than 0.05). However, CTX production in response to Sendai virus remained low. The extent to which CTX production by hairy cell leukemia mononuclear cells was reduced was proportionate to the observed decrease in monocyte counts. However, the degree to which CTX production improved after IFN treatment was significantly greater than the observed increase in monocyte counts. The major CTX induced by PHA in mononuclear cells of healthy donors and of IFN-treated HCL patients was identified as tumor necrosis factor-alpha.

Suppression of a polyclonal B-cell response by supernatants from the murine autologous mixed lymphocyte reaction

Previously, we have demonstrated that supernatants from autologous mixed lymphocyte (AMLR) cultures contain helper factors which can mediate the development of a cytotoxic T-cell response to hapten modified self. In the current study, the effect of AMLR supernatants on the humoral response was explored. BALB/C splenic non-T cells produced a large polyclonal antibody response to lipopolysaccharide (LPS), as measured in a Protein A SRBC plaque assay. Surprisingly, syngeneic AMLR supernatants suppressed the LPS-induced generation of plaque-forming cells. The presence of T cells in the stimulated cultures did not affect suppressor activity. The decreased response was not the result of a shift in kinetics, as maximal activity was observed on Day 4, whether or not AMLR supernatants were added. The AMLR culture supernatants were most effective in suppressing the plaque-forming cell response when added at the initiation of culture. AMLR supernatants added after 24 hr of culture resulted in only about 50% of maximum suppression. Supernatants added at 48 or 72 hr had no effect. Interferon-gamma (IFN-gamma) has been detected in AMLR culture supernatant and has been reported to suppress the development of plaque-forming cells in response to LPS. However, it is unlikely the suppressive activity observed in these studies is due to IFN-gamma. Dialysis of the AMLR culture supernatant against a pH 2 buffer for 24 hr or incubation at 70, 80, or 90 degrees C for 10 min, treatments that inactivate IFN-gamma, enhanced suppression. These results suggest that in addition to cytotoxic-T-cell helper factors, the cellular interactions in the AMLR induces the production of a stable mediator(s) which is able to directly suppress B cells at an early stage of their development into plasma cells.

Lymphocyte response to pokeweed mitogen in chronic lymphocytic leukemia

The response of lymphocyte subpopulations to pokeweed mitogen (PWM) was studied in normal volunteers and patients with B-cell chronic lymphocytic leukemia (CLL). Since unfractionated peripheral blood mononuclear (PBM) cells from CLL patients consist of a markedly increased proportion of B-lymphocytes and a decreased proportion of T-lymphocytes, enriched fractions of CLL B-cells and CLL T-cells were cultured in 1:1 proportions in autologous and allogeneic combinations with normal B-cell and T-cell-enriched fractions. Cultures containing normal B-cells with either autologous or allogeneic normal T-cells responded well to PWM. CLL T-cells were capable of providing a helper function for both proliferation and differentiation of normal B-cells, which was not significantly different from that provided by allogeneic normal T-cells. CLL B-lymphocytes were unresponsive to PWM when cultured in the presence of either autologous CLL T-lymphocytes or allogeneic normal T-lymphocytes. The responsiveness of CLL B-cells was not restored by the addition of normal peripheral blood monocytes to the cultures. These experiments indicate that there is an intrinsic B-cell defect which prevents CLL B-lymphocytes from responding to PWM.

Normal helper T-cell function in hairy-cell leukaemia

The function of peripheral blood T-lymphocytes was tested in a series of untreated patients with hairy-cell leukaemia (HCL). The in vitro T-colony forming capacity fell within the normal range in 20 of the 22 cases studied. No difference in colony growth was found between splenectomized and non splenectomized patients. The ability to induce differentiation of normal B-lymphocytes into antibody producing plasma cells, in a pokeweed mitogen (PWM) stimulated system, was similar to that of normal T-cells in all 6 cases studied. Both the T-colony growth and the helper capacity were unrelated to the distribution of T-lymphocyte subsets defined by monoclonal antibodies, despite an increase in OKT8+ cells (suppressor/cytotoxic phenotype) and a decrease in OKT4+ cells (helper/inducer phenotype) in 44% of the patients. The significance of these findings is discussed in relation to T-cell abnormalities previously described in other B-cell leukaemias, chiefly chronic lymphocytic leukaemia (B-CLL). The preserved T-cell function in HCL correlates well with the normal humoral immunity found in this disease.

Splenic alterations in hairy-cell leukemia: II. an electron microscopic study

Spleen from nine patients with hairy-cell leukemia (HCL) were studied for ultrastructural alterations. In all cases, hairy cells with typical ultrastructural characteristics were observed within splenic cords and sinuses. Hairy cells had numerous cytoplasmic processes that interdigitated with cytoplasmic processes of other hairy cells. Hairy cells also adhered to sinus endothelial cells and ring fibers and protruded into spaces between endothelial cells. Some normal sinuses were filled with aggregated hairy cells. Other sinuses appeared dilated. Many sinuses were lined by hairy cells that covered thinned endothelial cells and ring fibers. In these abnormal sinuses, endothelial cells were decreased and many appeared injured. The splenic cords were expanded by an infiltration of hairy cells and by large blood-filled spaces. These findings suggest that hairy cells adhere to many cell surfaces, produce endothelial cell injury and death, and impede the venous flow of blood in the spleen. All of the factors appear to influence the formation of the abnormal splenic sinuses and the blood-filled spaces that characterize HCL.