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Biomedical subjects

J C Howard

Publications and source records attributed to J C Howard.

At least 127 records · Page 7Linked to original sources
PubMed1974

Inhibition of experimental allergic encephalomyelitis in rats severely depleted of T cells.

Lewis rats depleted of thymus-derived cells (B rats) failed to develop either experimental allergic encephalomyelitis or antibody against myelin basic protein. Lewis B rats reconstituted with 690 x 10(6) thymocytes developed experimental allergic encephalomyelitis and levels of antibody against myelin basic protein comparable to those of controls. The Lewis B rat model should be useful in the analysis of the role of thymus-derived cell populations and antibody in the induction of experimental allergic encephalomyelitis.

Animals↗
PubMed1974

Specific positive selection of lymphocytes reactive to strong histocompatibility antigens.

Selected populations of thymus-derived (T) rat lymphocytes having specific immunological reactivity to chosen histocompatibility (H) alloantigens are found among the cellular products of the mixed lymphocyte interaction (MLI). Such specific selection seems to depend on (a) the antigen-induced proliferation of specific H antigen reactive cells (HARC), and (b) the disappearance of nonreactive cells from the cultures. When the surviving cells from this lymphocyte-antigen interaction are transferred into thymectomized, X-irradiated, marrow-reconstituted syngeneic recipients (B rats) which lack detectable T-lymphocyte functions, the lymphocyte populations subsequently recovered from the hosts possess the capacity to react in the MLI and in the graft-vs.-host (GVH) reaction, and the reactions have specificity for the original priming alloantigens. In addition, these findings identify the cell that reacts in the MLI with the GVH reactive cell.

Animals↗
PubMed1974

Be kind.

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Adolescent↗
PubMed1972

The life-span and recirculation of marrow-derived small lymphocytes from the rat thoracic duct.

These experiments describe the preparation of pure marrow-derived lymphocyte suspensions from the thoracic duct of thymectomized, irradiated rats reconstituted with bone marrow cells. The majority of marrow-derived cells were small lymphocytes morphologically indistinguishable from small lymphocytes in thoracic duct lymph of normal donors. Marrow-derived small lymphocytes (B lymphocytes) were a predominantly long-lived population; the frequency of short-lived B lymphocytes in the thoracic duct was not significantly higher than the frequency of short-lived small lymphocytes in normal lymph. B lymphocytes transferred to normal recipients recirculated from blood to lymph. The first appearance of intravenously injected B lymphocytes in the thoracic duct was delayed relative to lymphocytes from normal donors and there was no clear cut modal recirculation time. Nevertheless their recirculation over a 48 hr period after transfusion was of the same order of magnitude as that of lymphocytes from normal donors.

Animals↗
PubMed1972

Identification of marrow-derived and thymus-derived small lymphocytes in the lymphoid tissue and thoracic duct lymph of normal rats.

These experiments show that small lymphocytes from the thoracic duct of rats are normally a mixture of thymus-derived and marrow-derived cells, and define the traffic areas in lymphoid tissues through which the two populations recirculate. Thoracic duct lymphocytes were labeled in vitro with uridine-(3)H and their histological distribution in the lymphoid tissues of normal recipients was demonstrated by radioautography. Labeled lymphocytes occupied two adjacent areas distinguished by a marked difference in the intensity of labeling; heavily labeled cells were found in thymus-dependent traffic areas of lymphocyte recirculation, while lightly labeled cells localized in the thymus-independent follicular areas around germinal centers. A corresponding heterogeneity of uridine uptake among small lymphocytes from normal donors was demonstrated by sedimentation at 1 g; slowly sedimenting cells incorporated little uridine and localized in follicular areas after transfusion while rapidly sedimenting cells incorporated more uridine and localized in thymus-dependent areas after transfusion. Experimentally prepared marrow-derived small lymphocytes behaved in sedimentation studies and after transfusion like a pure population of the lightly labeled small lymphocytes in normal lymph. Artificially reconstituted mixtures of marrow-derived and thymus-derived lymphocytes were qualitatively indistinguishable from normal lymphocyte populations.

Animals↗