MicroELISA detection of thymosin alpha 1 released in thymic organ cultures.

Using a polyclonal specific rabbit anti-thymosin alpha 1 a highly sensitive enzyme-linked immunosorbent assay (ELISA) has been developed to measure thymosin alpha 1. Production of thymosin alpha 1 was detected in both thymic organ cultures and in mouse serum. The method is rapid (5 h), reproducible and easy to perform.

In vitro effect of thymosin alpha 1 on the expression of peanut agglutinin binding by murine thymocytes.

Thymosin alpha 1 induces the loss of PNA binding ability by subpopulation of thymic cells. This loss is probably due to an endocytic process. Nevertheless this disappearance is not a permanent one, suggesting a recycling of the PNA binding molecule. The cells that modulate their PNA binding sites after exposure to Thymosin alpha 1 are a small proportion of the total PNA+ thymocytes, indicating that not all thymocytes are susceptible to the thymic hormone Thymosin alpha 1. Conversely the exposure of thymocytes to Thymosin alpha 1 induces the disappearance of the binding sites for this ligand without further recycling, behavior expected for the receptor of a regulatory ligand. These results also indicate that the Thymosin alpha 1 and the PNA binding sites are on different molecules on the surface of the PNA+ thymocytes.

Effect of thymulin on intracellular cyclic nucleotides and prostaglandins E2 in peanut agglutinin-fractionated thymocytes.

Prostaglandin E2 (PGE2) and other selected agents which elevate intracellular cyclic AMP (cAMP) levels have been demonstrated to induce the appearance of surface markers in immature T lymphocytes. Thymic hormones, which are the natural inducers of these markers, have long been hypothesized to act through the increase of cAMP levels. We have approached this area of investigation by studying the effects of thymulin (a serum thymus-derived factor, coupled with Zinc) on intracellular cAMP and cyclic GMP (cGMP) levels (expressed as cAMP/cGMP ratio) and on the release of PGE2 in different thymocyte subpopulations. Thymocytes were fractionated by the peanut agglutinin (PNA) technique into cortical immature PNA+ and medullary mature PNA- thymocytes. The data presented in this report show that thymulin is able to increase the cAMP/cGMP ratio in PNA+ and in unfractionated thymocytes, depending on its concentration, but not in PNA- thymic cells. Conversely, it is able to increase the release of PGE2 by PNA- thymocytes but not by PNA+ and unfractionated thymic lymphocytes. These results are consistent with the hypothesis that thymulin could act through different mechanisms depending on the differentiation stage of its target cells. In fact, it could be suggested that immature T cells could be activated by thymulin thereby increasing the cAMP/cGMP ratio, whereas more mature T cells would be further differentiated by thymulin through enhanced release of PGE2.

[Effect of thymosin alpha 1 on prostaglandin release by murine lymphocytes]. / Effetto della timosina alpha 1 sul rilascio di prostaglandine da parte di linfociti di topo.

The effects on PGE2 release by lymphocytes obtained from adult thymectomized mice and from normal mice, after incubation with Thymosin alpha 1, were studied. Splenocytes from Tx mice release PGE2 at short time of incubation (15') using 4 micrograms/ml of Thymosin alpha 1 and at longer time of incubation (60'-180' using 4-8 micrograms/ml of Thymosin alpha 1. On the other hand thymocytes release the highest amounts of PGE2 after longer time of incubation (60'-180'). However lymphocytes obtained from normal mice do not release PGE2 amounts comparable with that released by the control samples. This effect shows an interesting interaction between thymic hormones and PGs.

[Effects of thymosin alpha l on some time-dependent functions in thymectomized mice]. / Effetti della timosina alfa 1 su alcune funzioni timo-dipendenti in topi timectomizzati.

The effects of a synthetic thymosin alpha1 on the azathioprine-sensitivity of spleen cells and on the thymic-like activity of serum from adult thymectomized mice, were observed. Thymosin alpha1 is able to restore the lowered levels of these T-dependent functions after in vivo administration.