Lymph nodes and human tumors (review)

Abstract

This review examines the crucial role of regional lymph nodes (RLN) in defense against tumor progression. RLN are one of the first major components of the immune system to come into contact with tumor cells or tumor-cell products and are important in the generation of tumor-directed immune responses. Involvement of RLN by tumor cells is a prognostic index of survival and a biological indicator of a more distant metastatic disease. Enlargement of lymph nodes as a consequence of the increase in the number of lymphoid cells, is a common finding in humans. These changes of cellular organization display the most decisive evidence of the existence of an immune response within a draining lymph node. The variety of cells mediating immune response to tumors are summarized briefly. The lymphocyte subpopulations involved reflect the nature of the response and may determine the outcome of the tumor-host interaction. The composition of the lymphocyte subpopulations can be recognized in tumor-draining lymph nodes by distinctive surface-membrane markers assessable by flow cytometry. In human patients with solid tumors limited quantification of the lymphocyte subpopulations within RLN has been carried out using this technique and the results indicated that an increase in B lymphocytes in tumor-reactive lymph nodes is marked in the adenocarcinomas (colon and breast) while in other tumors, such as melanoma and squamous cell carcinoma, this increase in B lymphocytes is less pronounced. The increased number of B lymphocytes in the reactive lymph nodes suggests the existence of an immune response involving interactions between T and B cells. B lymphocytes expression of CD80 appears to increase in some reactive lymph nodes to adenocarcinomas, possibly indicating the state of activation of CD80+ B cells, and their role as antigen-presenting cells. Any improvement in the antitumor activity of RLN would be important in the immunotherapy of cancer patients. The ability to generate a large number of tumor-reactive T lymphocytes is a critical requirement for adoptive immunotherapy. Tumor-draining lymph nodes (TDLN) are an excellent source of tumor-reactive T lymphocytes and the adoptive transfer of these cells is capable of mediating the regression of tumors established both in the lung and in the brain. Although cancers elicit a vigorous immune response during the early part of their growth, the immune response is soon downregulated, permitting progressive cancer growth. Furthermore, there are date suggesting the existence of immunosuppressive mechanisms within RLN in the antitumor response. However, there are no yet conclusive data concerning the characteristics of the response or its effectiveness.