In vitro and in vivo responses to thymosin in severe combined immunodeficiency

Irradiated fetal thymus transplantation in a patient with combined immunodeficiency with predominant T cell defect

A 6 month old boy was diagnosed as a case of combined immunodeficiency (with predominant T cell defect by previous classification). His T cell count was decreased, his B cell count in peripheral blood was increased, his serum IgG level was decreased, his serum IgM level was normal and the thymus was not evident on CT scans and magnetic resonance imaging. Administration of the thymus hormone, thymosin, led to a partial recovery of T cell function without normalization of the T cell count. At age 26 months the patient received an irradiated thymus transplantation from a 16 week old female fetus. After the transplantation, the T cell count (mainly CD4+ cells) increased by 50-70%. A mild graft-versus-host reaction (GVHR) occurred and several immunosuppressants were prescribed. Chromosome analysis showed that the T cells have both 46 XY and 46 XX karyotypes while the B cells have the 46 XY karyotype alone. His cellular immunity (skin tests, DNA synthesis, mixed lymphocyte reaction, cytotoxic activity and natural killer cell function) and his serum IgG level remained low. However, being on regular r-globulin therapy and oral anti-fungal drugs, he is now living normally with almost no trouble at age 6 years and 3 months. This case showed that irradiated thymus transplantation might be a useful method when an adequate donor for bone marrow transplantation is not available. The unexpected observation that the increased T cells were mainly CD4 may be related to the mild GVHR and the clinical improvement.

Thymic hormones in radiation-induced immunodeficiency. I. Induction of mature interleukin 1 responsive cell in the thymus by thymosin fraction 5

The restorative effect of thymosin fraction 5 (TF5) on the thymus of gamma-irradiated mice was examined. Four different mouse strains were used in this study since earlier work determined that the degree of response to TF5 is strain dependent. The responsiveness to comitogenic effect of interleukin 1 (IL-1) was used to measure the rate of recovery of immunocompetent cells in the thymus, since only more mature PNA-, Lyt-1+-2- medullary cells respond to this monokine. Contrary to several earlier reports that radioresistant cells repopulating the thymus within the first 10 days after irradiation are mature, corticosteroid resistant, immunocompetent cells, the thymic cells from irradiated mice in all strains used had greatly reduced responses to IL-1. Daily intraperitoneal injections of TF5 increased significantly the responses of thymic cells to IL-1 in 10- to 13-weeks-old C57Bl/KsJ, C57Bl/6, C3H/HeJ, and DBA/1 mice. Older mice, 5 months or more in age, of DBA/1 strain did not respond to treatment with TF5. However, C3H/HeJ mice of the same age were highly responsive. In conclusion, (1) cells repopulating the thymus within 12 days after irradiation contain lower than normal fraction of mature IL-1 responsive cells, (2) thymic hormones increase the rate of recovery of immunocompetent cells in the thymus, and (3) the effect of thymic hormones is strain and age dependent.

A placebo-controlled trial of thymic hormone treatment of recurrent herpes simplex labialis infection in immunodeficient host: results after a 1-year follow-up

Twenty-one immunodeficient patients with recurrent herpes simplex labialis (HSL) were randomly allocated to either the saline or the bovine thymus extract Thymostimulin (TS) group and treated for a period of 6 months. A total of 17 recurrences with a mean severity index of 266.2 +/- 192 in the TS-treated group versus a total of 62 recurrences in the placebo group (score 458.8 +/- 299.6) were observed after 12 months of follow-up. A significant increase of total WBC (P less than 0.05 versus control group), lymphocyte count, and T-cell number (P less than 0.001) were detected in the TS group after 6 months as well as after 12 months. In vitro lymphoproliferative responses to herpes simplex virus antigen and natural killer cell activity were also significantly higher (P less than 0.05) in the TS group, whereas no significant difference in antibody titers to herpes simplex could be detected between the two groups. TS may be potentially useful in preventing viral reactivation in immunocompromised hosts by potentiating cell-mediated immune responses. Further studies evaluating TS for prophylaxis of infection in patients at risk should be considered.

Thymosin fraction 5 does not accelerate reconstitution of immunologic reactivity after human marrow grafting

More than 1 year is required for immunologic function to recover following human marrow grafting. In an attempt to shorten the time required for immunologic reconstitution, 14 patients were treated with thymosin fraction 5 after transplantation. Two died before administration of thymosin could be completed. In the remaining 12 patients, immunologic studies were compared to those of patients who were transplanted but did not receive thymosin. While five patients had transient elevation of in vitro lymphocyte blastogenesis during thymosin treatment, results of other immunologic studies from patients treated with thymosin were similar to those from patients not treated. The subsequent development of graft-versus-host disease, major or minor infection, and leukaemic relapse was not different between the groups. Six patients are alive and five are well without problems; one has chronic graft-versus-host disease. We conclude that thymosin fraction 5 administered as described was not toxic. Although modifying some immunological parameters, thymosin did not appear to alter the incidence of graft-versus-host disease, infection or leukaemic relapse or to accelerate immunologic reconstitution.

Thymopoietin pentapeptide treatment of primary immunodeficiencies

26 patients with primary immunodeficiencies (3 infants with severe combined immunodeficiency [SCID] 3 with DiGeorge syndrome, 6 with T-cell defect or SCID with B cells, 4 with common variable hypogammaglobulinaemia and associated T-cell defect, 5 with ataxia-telangiectasia, and 5 with hyper-IgE syndrome) were treated with thymopoietin pentapeptide (TP-5) at a dose of 0 . 5 mg/kg daily for 2 weeks and then 3 times a week at 0 . 5 mg/kg for 10 weeks, 3 patients with DiGeorge syndrome and 3 with primary T-cell defect demonstrated pronounced clinical and immunological improvement during treatment. None of the patients with SCID and 3 of 6 patients with SCID with B cells or primary T-cell defect showed any clinical or immunological changes during therapy. In 5 patients with ataxia-telangiectasia clinical manifestations and immunological tests were unchanged by TP-5. Abnormality of T cells in cases of hyper-IgE syndrome was not corrected by TP-5 treatment.