Cloning, expression, and function of BLAME, a novel member of the CD2 family.

The CD2 family is a growing family of Ig domain-containing cell surface proteins involved in lymphocyte activation. Here we describe the cloning and expression analysis of a novel member of this family, B lymphocyte activator macrophage expressed (BLAME). BLAME shares the structural features of the CD2 family containing an IgV and IgC2 domain and clusters with the other family members on chromosome 1q21. Quantitative PCR and Northern blot analysis show BLAME to be expressed in lymphoid tissue and, more specifically, in some populations of professional APCs, activated monocytes, and DCS: Retroviral forced expression of BLAME in hematopoietic cells of transplanted mice showed an increase in B1 cells in the peripheral blood, spleen, lymph nodes, and, most strikingly, in the peritoneal cavity. These cells do not express CD5 and are CD23(low)Mac1(low), characteristics of the B1b subset. BLAME may therefore play a role in B lineage commitment and/or modulation of signal through the B cell receptor.

Epidermal growth factor: effect on circulating thyroid hormone levels in sheep.

Observations on the effect of thyroid hormones on mouse submaxillary gland epidermal growth factor (EGF) and on the complementary effect of EGF on cultured thyroid cells led us to examine the interaction between EGF and thyroid hormones in the whole animal, during and after 24 h of infusion of 3.3 micrograms/kg X h mouse EGF into 6 merino ewes. There was a profound depression of both circulating T4 and T3 levels, to less than 20% of saline-infused control values, extending beyond the end of infusion. Plasma TSH concentrations were unchanged during the first 8 h of the infusion, excluding the likelihood of a suppressive effect of EGF on the hypothalamic-pituitary axis. Serum rT3 and 3,3'-diiodothyronine, however, experienced a more transitory 6-fold increase. These findings are consistent with a dual inhibitory effect of EGF on both thyroid hormone secretion and peripheral metabolism.

Radioimmunoassay of 3-L-monoiodothyronine: application in normal human physiology and thyroid disease.

A RIA for 3-monoiodothyronine (3T1) using tritiated ligand, has been validated for measurement of extracted serum. The mean euthyroid level of serum 3T1 was 2.9 +/- 1.7 ng/dl. In thyrotoxic patients, the mean serum 3T1 was significantly higher: 6.2 +/- 3.9 ng/dl (P less than 0.001) and in hypothyroid patients, the mean level was 2.1 +/- 1.5 ng/dl, lower but not significantly lower than the mean euthyroid level (P greater than 0.05). The mean serum level in severely ill patients was 2.5 +/- 1.5 ng/dl (P greater than 0.05) and in cord blood was significantly higher at 9.1 +/- 2.6 ng/dl (P less than 0.001). The appearance of 3T1 within 5 min in two normal volunteers after iv injection of 3,3'-diiodothyronine was followed over 2 1/2 h. Thus 3T1 is a normal constituent of human plasma and is derived from 3,3'-diiodothyronine. Its concentrations appear to be severalfold higher than those reported for 3'T1.

Effect of iodination of a village water-supply on goitre size and thyroid function.

An iodinator was fitted to the existing gravity-fed water-supply of a remote village in Sarawak, Malaysia, where goitre was endemic. Within nine months, the prevalence of goitre had been reduced from 61% to 30%, with 79% of goitres showing visible reduction in size. All subjects were clinically euthyroid before and nine months after the start of iodination, although pre-treatment serum thyroid-stimulating hormone (TSH) concentrations varied from normal up to 24 mU/l. Before treatment basal serum triiodothyronine (T3) and thyroxine (T4) concentrations were typical of endemic goitre with a low mean serum T4 (80 +/- 30 [SD] nmol/l) and a slightly raised mean serum T3 (2.3 +/- 0.7 nmol/l). After iodination, circulating TSH concentration was generally undetectable (less than 0.1 mU/l), mean T3 concentration was unchanged, but the mean T4 rose significantly to 109 +/- 41 nmol/l (p less than 0.01). Urinary iodine concentrations fluctuated; this largely reflected intermittent blockage of the iodinator, but concentrations became consistent with a return to the iodine-replete state. There was no evidence of the Jod Basedow effect in the group studied. Iodinated water was more convenient to distribute than iodised salt and is less likely to cause Jod Basedow phenomenon than are injections of iodised oil. Moreover, iodination of water is effective in killing most microorganisms and this additional benefit could contribute significantly to village health.

Measurement of 3'-monoiodothyronine in human serum.

An heterologous radioimmunoassay for measurement of 3'-monoiodothyronine (3'T1) has been developed using pure 3'T1 as standard, (125I)DL3'T1 and an anti 3,3'L-diiodothyronine antiserum. The assay utilizes Sephadex G25F minicolumns to separate 3'T1 from other endogenous iodothyronines. 8-anilino-1-naphthalene sulphonic acid was used to inhibit binding of 3'T1 to serum binding proteins. Sensitivity was approximately 3.2 pmol/l. The mean serum 3'T1 concentration was 7.4 pmol/l in normal subjects, 30.8 pmol/l in thyrotoxic patients, 4.1 pmol/l in hypothyroid patients, 23.2 pmol/l in patients with severe non-thyroidal illness and 109.8 pmol/l in cord blood. Increased levels of 3'T1 were found in two normal volunteers who were injected with 3,3'T2, demonstrating that 3'T1 is derived from 3,3'T2 in extrathyroidal tissues. These studies suggest that 3'T1 is a minor iodothyronine metabolite in the human. It is unlikely to have significant biological relevance.

Radioimmunoassay of progesterone in unextracted serum.

We describe a rapid, precise radiommunoassay for progesterone in 25 muL of unextracted serum. Progesterone is released from its binding protein by adding an optimal amount of cortisol, which binds to the same protein (cortisol binding globulin) as progesterone. The amount of cortisol required does not cross react with the specific progesterone antibody used. This approach considerably shortens assay time and removes a tedious and imprecise stage in the conventional assay of serum progesterone. Results correlated well (r = 0.97) with a method involving organic solvent extraction of progesterone from serum. During the two years we have used this method in a busy diagnostic endocrine laboratory, the between-assay precision (CV) for low-, medium-, and high-concentration quality control sera was 12, 7, and 9%, respectively. Data from participation in an independent external quality-control program verified the adequacies of the method.

Effects of triiodothyronine administration in patients with chronic renal failure.

Clinically euthyroid patients with severe, chronic, non-thyroidal illnesses usually have decreased serum total and absolute free T3 concentrations. Since T3 is the metabolically more active of the two thyroid hormones, it has been suggested that these patients may be hypothyroid and thus may benefit from T3 therapy. To test this hypothesis, five patients with chronic renal failure requiring maintenance haemodialysis were treated with 5 microgram T3 eight hourly, increasing at three weekly intervals to 10 microgram eight hourly, 20 microgram eight hourly and finally 30 microgram eight hourly. The mean +/- SD serum T3 level did not change over the 12 week period (1.42 +/- 0.17 vs. 1.41 +/- 0.26 nmoll-1 whilst the mean serum T4 and TSH levels fell from 87.0 +/- 15.2 to 47.5 +/- 18.8 nmoll-1 and 1.9 +/- 0.9 to 1.3 +/- 1.6 mUl-1 respectively. Only the change in T4 levels was significant (P less than 0.005). A significant decrease in mean serum T4 levels was apparent even after the treatment period with 5 microgram T3 eight hourly (87.0 +/- 15.2 vs. 51.2 +/- 15.7; P less than 0.005). The mean fasting serum triglyceride level fell from 1.16 +/- 0.74 to 0.94 +/- 0.74 mmoll-1 (P less than 0.05) and the mean fasting serum cholesterol level fell from 6.06 +/- 1.13 to 4.69 +/- 1.10 mmoll-1 (P less than 0.05). There were no subjective improvements in any of the patients. From the marked changes in serum T4 levels during the administration of T3, it is concluded that, prior to treatment, the patients were biochemically euthyroid and not hypothyroid and thus did not require T3 therapy.

Inhibition of conversion of thyroxine to triiodothyronine in patients with severe chronic illness.

Many clinically euthyroid patients with severe, chronic, non-throidal illnesses (i.e. sick euthyroid patients) have very low circulating concentrations of total and absolute free triiodothyronine (T3), low-normal concentrations of total thyroxine (T4), elevated concentrations of absolute free T4, and circulating concentrations of thyrotrophin (TSH) that are either normal or subnormal. This study was undertaken to elucidate the mechanism of the low circulating T3 concentrations. The disappearance rate of 125 I-T3 from the circulation of five representative sick euthyroid patients was studied and found to be slower, but not significantly so, compared with three control subjects, thus excluding an increased destruction rate as the cause of the low T3 levels. A selective decrease of T3 secretion from the thyroid gland of these patients was also excluded by the results of TSH stimulation tests. Inhibition of extra-thyroidal conversion of T4 to T3 was suggested by studies of the thyroid function in a hypothyroid woman with a Grade IV lymphoma on T4 replacement therapy. When the lymphoma was in remission, her circulating T3 concentration was 2-55 nmol/l but when it relapsed it fell to 0-55 nmol/l. The T4 concentrations were 124-7 nmol/l and 126 nmol/1 respectively. Decreased monodeiodination of T4 to T3 in sick euthyroid patients was confirmed by paper chromatography of extracted serum obtained 48 h after an i.v. injection of 125 I-T4 into two severely ill patients from the intensive therapy unit and a control subject. Peaks of radioactivity corresponding to 125 I-T4 and 125 I-T3 were detected in the control subject, but only a single peak corresponding to 125 I-T4 was detected in the ill patients.