28 human and 60 experimentally stimulated rabbit lymph nodes were studied by means of light microscopy and immunofluorescence. 21 of the 28 human lymph nodes showed well-developed germinal centers. IgM, IgG, and the beta(1C) component of complement were found in the same distribution within germinal centers when examined in serial cryostat sections. 36 rabbits were stimulated with Brucella antigen, and 24 rabbits with BSA. A strikingly consistent correlation between distribution and appearance of specific staining for rabbit beta(1C), IgM, and IgG was observed; when lymph nodes were stimulated with BSA, antigen and specific antibody were present. Treatment of unfixed sections with citrate-buffered saline at low pH resulted in complete elution of immunoglobulins, beta(1C), and BSA from rabbit germinal centers, and in marked diminution of IgG and IgM in human germinal centers, while at the same time plasma cells remained strongly fluorescent. Specific selective fixation of heterologous (human) complement in rabbit germinal centers positive for beta(1C), IgG, IgM, and BSA was also obtained. These data present strong evidence for the existence within germinal centers of antigen-antibody complexes which fix at least the beta(1C) component of complement in vivo. The possibility of complete elution of immunoglobulins from rabbit germinal centers can be taken as evidence that, at least for 20 days after primary and secondary stimulation, a major component of the immunoglobulins present in germinal centers is not produced locally but accumulates at the surface of cells.

Animals↗

PubMed1969

Carcinogen-induced tumors of the thymus. IV. Humoral influences of normal thymus and functional thymomas and influence of posthymectomy period on restoration.

A progressive decrease of the restoring effectivity of syngeneic or allogeneic thymus and functional thymoma grafts was observed when the treatment of neonatally thymectomized mice was delayed. Early treatment (5-20 days postthymectomy) was effective, while the number of restored animals was markedly decreased after late treatment (30-50 days postthymectomy). Similar results were obtained with subcutaneous or intraperitoneal thymus grafts and with thymus grafts within cell-impenetrable diffusion chambers. After the onset of the postthymectomy-wasting syndrome the only successful treatment was the implantation of multiple thymus grafts. On the other hand, single thymus grafts, thymoma grafts, or thymus or thymoma within diffusion chambers were ineffective. When spleen cells from 5-day old or 45-day old neonatally thymectomized animals were given in association with thymoma grafts, only the cells derived from the 5-day old thymectomized mice proved effective in restoring wasted thymectomized hosts. These results suggest that a population of cells sensitive to the action of the thymus decreases progressively with time in the absence of thymic function.

Age Factors↗

PubMed1969