No abstract

The grafting of a single spleen colony obtained from irradiated mice protected with 12-day fetal liver will reconstitute the lymphopoietic and erythropoietic system of irradiation-deprived syngeneic recipients. Using this experimental model, the early events during the ontogenic development of the immune system were studied in CBA mice. Cells capable of binding radio-iodine labeled S. adelaide polymerized flagellin were first detectable after 18 t o 20 days of lymphopoiesis starting from presumably a single stem cell. However, antibodyforming cell production after immunization against the same antigen was not demonstrable until days 19 t o 26. The same sequential development of antigen recognition (by rosette formation) followed by immune reactivity was observed for sheep red cell antigens, both events occurring later than those for POL. Our observed requirement for the ontogeny of an antigen-recognition spectrum is compatible with Jerne's theory on the generation of antibody diversity. Edmonton

Background:The distribution of muscle spindles (Sps) in a small muscle of simple architecture, the capsularis at the cat's hip joint, was quantified to reveal the patterns of proprioceptive representation in the transverse and sagittal planes as well as to model the effect a local disturbance in muscle length would have on total Sp discharge.Methods: Locations in serial cross-sections of the 32 and 38 Sps in 2 muscles, 1 perfused with the hip joint flexed and the other extended, were plotted, and their patterns of integrated sensitivity calculated assuming that (1) the discharge rate of a Sp afferent varies linearly with change in length along the Sp's axis, and (2) that within a local disturbance produced by contraction of a motor unit (MU), lengths decrease either linearly or as the square of the distance from its center.Results: The isomeric pattern of ''integrated, total Sp representation on cross-section'' showed two peaks of sensitivity in the half of the muscle that had been next to the joint capsule, offset by low representation in a small, central area and along the extensive zone bordering the laterally facing ''superficial surface.'' The equivalent radius of an idealized symmetrical MU territory was estimated from distributions of the few fast, oxidative-glycolytic fibers found in two muscles, and the effect of a MU's contraction on net Sp discharge predicted when the unit was positioned at distinctive sites within the pattern. As an index of Ia and II afferent representation in the sagittal plane, the distribution of the nucleated regions of Sps and the summed lengths of segments of Sp axial bundles and capsules, respectively, within successive 1-mm segments of the muscle were graphed.Conclusions: The longitudinal representation and structure of the muscle are not suited for reflex adjustment of differences in length along the muscle. The isomeric pattern of high relief in the transverse plane suggests that in this ϳ0.2 g muscle, the localization of myotatic reflexes might be accommodated but the need for adjustment in activation of MUs seems minimal. This is because the muscle is not compartmentalized, its fibers extend between the muscle's origin and insertion, their angle of pinnation is low, and greater than 90% are of slow type. The distribution of Sps is consistent with gauging length of the entire muscle and hence angulation at the hip joint. Anat.

In solid phase indirect radioimmunoassay (IRIA) antiviral immunoglobulins (Ig) bind specifically to the viral antigen fixed onto wells of microtiter plates. Radioactively labeled (125I) anti-Ig can be used to detect these antiviral antibodies. The sensitivity of the IRIA depends on the amount of antigen in the microtiter wells and the concentration of the 125I-labeled anti-Ig used. To standardize the assay, a method of antigen titration in the IRIA was devised, using parainfluenza type 1 viruses as antigens. The IRIA provides a means to titrate viral antigens with different biologic activities and antibodies against them. A binding inhibition test (BIT) based on IRIA allows the antigenic analysis of different virus strains, as is demonstrated for two closely related parainfluenza type 1 virus strains.

Lymph nodes and blood from human subjects without neurologic disease, as well as lymph nodes from normal guinea pigs, contain lymphocytes capable of binding radiolabeled encephalitogenic basic protein of human myelin. In man, the number of such cells is comparable to that of cells binding a foreign antigen, radioiodinated flagellin of Salmonella adelaide. These observations lend support to the opinion that “forbidden clones” of lymphocytes, recognizing autoantigens, do exist in apparently normal animals.