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Pokeweed mitogen (PWM)-driven in vitro synthesis of antibodies to the acetyicholine receptor (PSA) was study in non-thymoma patients with myasthenia gravis. In a group of 46 patients, the occurrence of PSA was related to the presence of the thymus or, in operated patients, the absence of a clinical effect of thymectomy. Sixteen patients were followed before and soon after thymectomy. PSA disappeared in all patients, at least temporarily, between 6 weeks and 1 year afterwards, independent of the clinical course and eventual clinical effect of the operation. A recurrence was found only in one of the five patients who derived no benefit from the operation. These findings support the hypothesis that the therapeutic effect of thymectomy can be explained by removal of a source of autoreactive lymphocytes. There was no correlation between the changes in serum levels of a-AChR and clinical improvement, suggesting a minor role of circulating peripheral blood lymphocytes (PBL) and the thymus in the total production of a-AChR. [ABSTRACT FROM AUTHOR]

Cultures of pure epithelial cells have been obtained from human thymus. Incubation of spleen cells from adult thymectomized mice on these cultures rendered RFC sensitive to inhibition by anti-theta serum. whereas no effect was obtained with fibroblasts or spleen cell cultures. The fact that theta conversion was obtained when spleen cells were incubated in the thymic culture placed within a Millipore chamber indicates that theta conversion was due to the effect of a immoral factor. [ABSTRACT FROM AUTHOR]

The effect of cortisone acetate on specific cell mediated immunity in mice was investigated using contact sensitivity to oxazolone. A long-acting cortisone acetate preparation was found to be much more effective than a soluble preparation in suppressing temporarily the recall response to oxazolone. The long-acting preparation was also effective in inhibiting the induction of sensitivity when injected before (but not after) oxazolone. Removal of the thymus either before or after sensitization did not significantly enhance the effects of cortisone acetate, and it is therefore suggested that cortisone acetate acts independently of the thymus-derived lymphocyte population. [ABSTRACT FROM AUTHOR]

Irradiation following adult thymectomy results in a reduction of the size of the T-cell pool of mice as adjudged by the number of blood cells which are found responding to PHA. Recovery of the number of cells in the pool does not occur on a large scale over a period of 70 days in the absence of thymus tissue. [ABSTRACT FROM AUTHOR]

Normal, 'deprived' (thymectomized, irradiated, bone marrow injected) and 'reconstituted' (thymectomized, irradiated, bone marrow injected, thymus grafted) CBA mice have been tested for their ability to respond to the contact sensitizing agent, oxazolone. The test involved painting the ear of a previously sensitized animal and subsequently measuring alterations in ear thickness. .A sensitized condition could be detected in the normal and reconstituted mice after either one or two sensitizing contacts with oxazolone but in the deprived animal little or no sensitivity could be detected. It is concluded, that the thymus influences the development of contact sensitivity probably by provision of a population of reactive cells. [ABSTRACT FROM AUTHOR]