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Serum from 21 patients with lymphoblastic leukemia, five with myeloblastic leukemia and 30 age matched control subjects tested for thymic hormone activity in an assay that measures the induction of T cell surface antigen. This activity was subnormal in serum from 10 of 16 patients with untreated lymphoblastic leukemia (p less than 0.001) but was within the normal range when the leukemia was in remission. Low inductive activity was associated with an inhibitor of T cell induction which was less than 30,000 daltons in molecular size and interfered with induction by purified thymopoietin plus a high concentration of ubiquitin or by normal serum alone.

Sera from 13 patients with mycosis fungoides and 2 with Sezary syndrome were tested for activity that induces lymphocyte differentiation. Induction of Thy-1.2 antigen and surface immunoglobulin were used, respectively, to measure T- and B-cell differentiation. The indicator cells were null lymphocytes from the spleens of congenitally athymic nude mice. Normal serum induced some T-cell but no B-cell differentiation. The T-cell-inducing activity was ascribed to thymic hormone and declined with advancing age. A totally different pattern emerged with patient serum. T-cell-inducing activity was significantly more active than in normal serum (p less than 0.001). This activity did not decline with advancing age and was not inhibited by a concentration of ubiquitin, which blocks nonspecific beta-adrenergic induction. B- cell-inducing activity was also present. This novel serum factor (or factors) is a potent inducer of T- and B-lymphocyte differentiation and is associated with neoplastic lymphoproliferation of the T-cell series.

Serum thymic hormone activity was measured in 36 patients with myasthenia gravis and in 10 control subjects from each age decade. In all 25 patients under 50 years of age results were within, or close to, the normal range. Activity at levels considered normal for juveniles was detected in 10 of the 11 older patients whereas levels normally decline in older subjects. One week after thymectomy, 13 of 17 patients (76 per cent) had no demonstrable serum thymic hormone activity. However, 10 months or longer after thymectomy only five patients (30 per cent) lacked thymic hormone activity in the serum. There was a significant correlation between clinial improvement and sustained lowering of serum thymic hormone activity after thymectomy.

Complement dependent cytotoxicity to malignant melanoma tumor cells was demonstrated in incubations that included rheumatoid factor (RF) positive plasma and normal plasma. Cytotoxicity was not demonstrated to cells from a number of normal tissues. The phenomenon involved coating of tumor cells with immunoglobulins and complement fixation. The activity in RF positive plasma was present in high titer an may not be RF. The activity in normal plasma was present in low titer, was found in plasma from eight out of 11 healthy subjects and may be a naturally occurring antibody. This previously undescribed humoral cytotoxicity system may participate in tumor host interactions, especially after therapy, when the majority of patients become RF seropositive.

Circulating thymic-hormone activity was assayed by measuring Thy 1-2 antigen induction on null lymphocytes from athymic mice incubated with human plasma or serum. Plasma from 19 normal children aged under 10 had inductive activity equivalent to 10-6-16-2 ng thymopoitin/ml. Plasma from 15 infants were severe combined immuno-deficiency, 2 of whom had appreciable immunoglobulin synthesis, and from 2 infants with DiGeorge syndrome had little or no inductive activity. Successful reconstitution with thymus or bone-marrow grafts and with red-cell infusions (if adenosine-deaminase deficiency is present) was followed by a rise in circulating thymic-hormone activity.

In this survey for rheumatoid factor (RF) seropositivity on patients with neoplasms, an 85% rate of positive screening tests was recorded under certain circumstances. This high rate of RF seropositivity occurred after irradiation and/or chemotherapy of breast and lung cancers. Treated patients with breast cancers who had no evidence of residual tumor had an 89% rate of positive RF tests. Conversely, the incidence of RF seropositivity was low among untreated patients with similar tumors and treated patients with glioblastomas or multiple myeloma. The administration of cytotoxic drugs (e.g., azathiprene) was not itself associated with RF production even in renal allograft recipients. The data indicate that RF production occurs frequently after therapy of certain tumors and suggest that in these circumstances RF may be an expression of tumor-host interaction.

Thymopoietin is a thymic hormone that induces differentiation of thymocytes from precursor cells which arise in hemopoietic tissues. This paper describes a sensitive in vitro assay for the induction of Thy 1.2 antigen on null lymphocytes from germ-free athymic (nu/nu) mice. The sensitivity and specificity of the bioassay were increased by adding high concentrations of ubiquitin (a nonspecific inducer) to the induction incubations. The bioassay was sufficiently sensitive to detect thymopoietin at less than 0.25 ng/ml. A dose-response relationship was shown between thymopoietin concentration and the percentage of cells induced to express Thy 1.2 antigen. When normal human plasma was assayed, induction was registered with activity corresponding to thymopoietin at greater than 1 ng/ml in plasma from infants or young adults. Activities in the thymopoietin range of 0.25 ng/ml were registered with plasma from healthy subjects over 50 years of age. Thymectomy was followed by loss of this inductive activity from the plasma. This bioassay permits clinical studies on T (thymus-derived) cell inducers released by the human thymus into the circulation.

Zinc deficient humans and animals have depressed thymic mass and increased susceptibility to infection. In the present studies, we investigated the relationship between cellular immunity, thymic hormones, and serum zinc levels in 19 patients with common varied immunodeficiency. Five (26%) had serum zinc levels 2 SD below normal and 11 (58%) had abnormally low lymphocyte proliferation to at least one mitogen. A significant statistical correlation between zinc levels and lymphocyte proliferation to phytohemagglutinin and concanavalin A was identified. Forty-two percent had abnormally low levels of facteur thymique serique and 74% had low levels of thymopoietin, although no statistical relationship between the levels of these hormones, zinc levels, or lymphocyte proliferation could be identified. Three patients with the most profound zinc deficiency had substantial increases in thymic hormones after zinc repletion, and two had complete resolution of intractable diarrhea. A therapeutic potential of zinc for certain patients with hypogammaglobulinemia is suggested.

Serum T-cell-inducing activity was measured in sera from 25 young patients with systemic lupus erythematosus and 30 age-matched controls. Subnormal activity was recorded on 14 of the patients. The occurrence of low values correlated with the presence of disease activity (P < 0.05). In individual patients higher values were recorded when the disease was inactive than during periods of disease activity (P < 0.001). Subnormal serum thymic hormone activity appeared to be due to reduced serum content rather than the presence of an inhibitor.