Immunological reconstitution of T-cell-deprived mice. I. Inability of thymosin to restore spleen cell mitogen and tumor allograft response

Survey of thymic hormone effects on physical and immunological parameters in C57BL/6NNia mice of different ages

Immunosenescence occurs with aging, which is seen in decline in response to mitogens PHA, ConA, decline in cell-mediated immunity, increase in anemia, and increase in autoimmune antibodies to erythrocytes and DNA. These studies compared FTS, TP5, TM4, and TF5 in C57BL/6NNia mice. Mice aged 4, 26, 52, 78 and 104 wk were treated with various hormones 5x/wk for 3 wk and monitored for hormonal effects on weight; hematocrit; peripheral blood, spleen, and thymic cell numbers; spleen and peripheral blood cell mitogen responses to PHA, ConA, LPS; IgM hemolysin autoantibody; and cell-mediated cytotoxicity to P815 allogenic cells. Hormone treatments altered mitogen responses, enhanced IgM hemolysin autoantibody production, and modulated cell-mediated immune responses. The effects were not consistent for every hormone. There was a tendency for enhancement in younger mice and suppression in older animals. Treatment with FTS showed the greatest changes in either enhancing or suppressing the different parameters measured. The hormonal effects appeared to be age specific in that certain activities were altered for certain age groups but not in others. Hormone treatment did not restore any immune parameters in old mice to the level of young animals. In general, the different hormones did not consistently produce the same effects in C57BL/6NNia mice of different age groups. Even though all animals received from National Institutes on Aging (NIA) animal models program were held under strictly controlled conditions, intrinsic variations between cohorts of different ages are difficult to control. Cohorts of aging animals tested at different times might be intrinsically different. This inherent variability in the cohorts could affect the range of activity, specificity and reproducibility of hormone effects in vivo. Most importantly, it should be emphasized that cross-sectional data identifies age differences rather than age changes. There is no assurance that age changes in any individual or in all subpopulations follow this pattern. In our studies only healthy animals were used. Old, sick, or tumor-bearing animals were culled out prior to being sent to us. Therefore, the 78- and 104-wk-old mice represent selected healthy cohorts. The age changes that take place can be answered only from repeated measurements made in the same individual over time.

Effect of thymic hormone treatment on several immune functions of nude mice

Studies of the effect of short-term, intense treatment with thymic hormone on mitogen response, cytotoxicity to EL-4 lymphoma and natural killer cell (NK) activity was investigated Balb/c nude mice (about 12-16-week-old) were treated 5 times per week for 3 weeks with: Facteur Thymic Serique (FTS) and Thymopentin (TP5, Thymopoietin 32-36) at 1 microgram and 10 ng; TM4 1 ng (an enzyme resistant variant of FTS); Thymosin Fraction V (TF5), 10 and 1 microgram; and 0.1 ml saline, and killed 2 days after the last treatment. The animals were monitored for changes in weight, hematocrit, peripheral blood lymphocyte (PBL) and spleen mitogen response. Additional groups of nude mice were immunized with 1 x 10(7) 5000 R irradiated EL-4 cells 10 days before sacrifice and tested for the presence of cytotoxic T-lymphocytes (CTL). The results show that weight and hematocrit were similar among the groups. Treatment with FTS significantly elevated the number of PBL. Spleen stimulation in mice treated with 1 microgram TP5 was depressed to mitogen concanavalin A (ConA) and lipopolysaccharide (LPS) stimulation. The phytohemagglutinin (PHA) response was not different among the treatment groups. The PBL mitogen response to ConA and LPS was generally increased over saline control in the hormone treated groups but was not statistically significant. The PHA response was only slightly elevated. No CTL was generated in nude mice in any of the groups. However, there was a statistically significant general depression of NK activity in all of the hormone treated animals compared with saline. The results indicate that the basic differentiation defect of the T-cells of nude mice cannot be restored to full functional activity by short-term treatment.

The effect of experimental conditions on the assessment of T cell immunomodulation by biological response modifiers (thymosin fraction five)

The coculture of spleen cells with specific antigens in the presence of thymosin fraction five (F5) results in the stimulation of the lymphocyte response. To observe the stimulation, a suboptimal responder-to-stimulator ratio must be utilized. Suboptimal assay conditions also are needed in immunization challenge studies in which thymosin F5 acts as an effective immunoadjuvant. The data reported here suggest that to study the efficiency of a biological response modifier, suboptimal assay conditions are best for observation of immunomodulation. We also report that thymosin F5, in addition to exhibiting adjuvantlike activity for T cells, is stimulatory in assays of mixed lymphocyte response and in the in vitro stimulation of cytotoxic T effector cells, following a mixed lymphocyte-tumor culture.

Immunomodulation and therapeutic characterization of thymosin fraction five

In this report we describe the characterization of the immunomodulatory efficiency and therapeutic properties of thymosin fraction five (F5). We consistently observed the immunostimulation of T-cell activity in assays of allogeneic mixed lymphocyte response (MLR) and the development of cytotoxic effector cells in an allogeneic mixed lymphocyte tumor response-cell-mediated cytotoxicity assay (MLTR-CMC). No induction of suppressor cell activity was observed. Thymosin F5 also acted successfully as an adjuvant when admixed with irradiated tumor cells. We were unable to demonstrate either NK cell or macrophage activation by thymosin F5. Therapeutic protocols using thymosin F5 and directed against pre-existing experimental and spontaneous metastases, had a significant immunotherapeutic potential.