Lymphocyte Response to Antigens. A. Afferent Side of... : Transplantation (original) (raw)

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Lymphocyte Response to Antigens. A. Afferent Side of Sensitization Arc

RESPONSE OF LYMPHOCYTES TO ANTIGENS

Department of Immunology, Institute of Dermatology, St. John's Hospital for Diseases of the Skin, Homerton Grove, London, England

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Abstract

Many differences between the cellular changes, which take place during the induction of delayed hypersensitivity and humoral antibody formation, could be explained on the basis of an initial difference in the site of contact between the lymphocyte and antigen. Lymphocytes picking up a stimulus from fixed antigen in the periphery would migrate down to the regional lymph node, arriving in the cortex. Here they would find the right milieu for differentiation and proliferation and as a result of their proliferation paracortical areas would be formed. This process would appear to be influenced by the thymus, so that in neonatally thymectomized animals this process cannot take place. After a period of at least four days progeny lymphocytes will leave the lymph node with the capacity of both continuing the state of sensitization probably by proliferation in other lymphoid tissues. These progeny lymphocytes would also contain a “recognition factor” possibly related chemically to an immunoglobulin. If during circulation through the periphery they come into contact with antigens they will be able to initiate a process resulting in a state of inflammation or if the antigen is part of a target cell, destroy it.

If the antigen is not fixed in the periphery but soluble it will itself drain down into the regional lymph node reaching the corticomedullary junction. Here it will stimulate the transformation of lymphocytes into plasma cell precursors, at this site and in the medullary cords. As a result of this humoral antibodies will be formed. Antigen will also be trapped in lymph follicles where it will react with soluble antibody present in the lymph node and this antigen/antibody interaction could be sufficient to cause the massive cell proliferation and cell death found in germinal centers.

A limited amount of antigen would also travel down to the draining lymph nodes during the development of contact sensitivity and transplantation immunity. This is why there is also limited antibody formation as well as delayed hypersensitivity occurring as a result of these immunologic stimuli.