Restoration of specific immunological virginity

Lymphocyte traffic through lymph nodes during cell shutdown

Antigenic challenge of lymph nodes in sheep has marked effects on lymphocyte traffic through lymph nodes. The non-specific effects include a marked reduction in lymphocyte output in efferent lymph without a corresponding decrease in lymph flow--a phenomenon known as cell shutdown. With certain antigens there is a total disappearance of B lymphocytes during cell shutdown. The phenomenon can be reproduced in unprimed lymph nodes whenever localized complement activation occurs within the node. This also induces the release of prostaglandins, particularly PGE2. These results suggest that cell shutdown might be a two-step process involving both complement and prostaglandins. Repeated stimulation of nodes with antigen also has considerable effects on the traffic of antigen-specific lymphocytes. Antigen localized within the node can promote the selective entry into the node of T lymphocytes specific for the challenge antigen. Consequently there is a net loss from the whole animal of T cells reactive to the challenge antigen. These results are discussed in relation to lymphocyte recirculation through antigen-stimulated lymph nodes.

Protection against allergic encephalomyelitis by recruitment of myelin basic protein reactive lymphocytes into a single lymph node

The efferent popliteal lymphatic of sheep was cannulated and sheep myelin basic protein (BP) was repeatedly injected into the drainage site of that popliteal node. All the recirculating lymphocytes leaving the node were removed from the sheep via the efferent cannula. Sheep undergoing such chronic stimulation and drainage failed to develop allergic encephalomyelitis when challenged with an encephalitogenic inoculum in the contralateral leg. Chronic stimulation without subsequent removal of lymphocytes did not protect animals against challenge. These results suggest that protection is due to the stimulation, recruitment and removal of specific BP reactive cells from the recirculating lymphocyte pool. Possible therapeutic applications in multiple sclerosis are discussed.

Passive transfer of tuberculin sensitivity from anergic mice

Mice heavily infected with Mycobacterium bovis BCG rapidly became anergic to cutaneous injection with tuberculin. Evidence is presented suggesting that this anergy reflects an adaptive physiological change within the host in which antigen-reactive Thy-1.2+ cells become sequestered in central lymphoid tissues, with a concomitant reduction in the circulating pool. No evidence could be provided to support the suggestion that anergy was a consequence of an acquired immunosuppressive mechanism.

Specific selection of antigen-reactive lymphocytes into antigenically stimulated lymph nodes in sheep

Sheep were primed to a variety of antigens and the efferent lymphatic from a popliteal lymph node was cannulated. The cannulated node was challenged repeatedly with PPD and all the lymph and cells removed from the animal. During this time the PBL were monitored for reactivity to all antigens (purified protein derivative of tuberculin [PPD], johnin, and keyhole limpet hemocyanin [KLH]) by the vitro transformation assay. The response of these cells to PPD was found to be gradually eliminated after repeated challenge of the cannulated node with that antigen. The response to the other antigens was unimpaired. No depletion of this response to PPD occurred in cannulated sheep when the antigen was given into a noncannulated node. In vivo delayed-type hypersensitivity skin test and helper T cell assays confirmed that there is a specific selection of antigen-reactive cells from the recirculating lymphocyte pool into antigen-stimulated lymph nodes.

Clonotype patterns of antibodies released by single lymph nodes

Experimental primary, secondary and tertiary stimulation with streptococcal vaccine of isolated lymph nodes in vivo in the sheep model induces largely persistence of anti-group polysaccharide antibody clonotype patterns with the rare occurrence of additional clonotypes demonstrable after secondary stimulation persisting during the tertiary stimulus. It is not clear whether these additional clonotypes are the products of mutants or whether they pre-existed and were demonstrable only after a secondary stimulus, because of threshold concentrations required for identification. Further, isolated contralateral popliteal and prescapular lymph nodes of individual sheep share completely overlapping clonotype patterns during experimental primary anti-polysaccharide antibody responses indicating an identical repertoire of specific clonotypes under this condition of responsiveness.