ORIGINAL ARTICLE Beatriz Lores-Vazquez Margarita Pacheco-Carracedo Josefina Oliver-Morales Purificacio ´n Parada-Gonzalez Francisco Gambo ´n-Deza Received: 4 January 1996 / Accepted: 28 May 1996 AbstractmIn order to study the host immune response to tumours, previous knowledge of the cellular composition of regional draining lymph nodes is necessary. Enlarged re- gional lymph nodes are a common finding in colon and gastric adenocarcinomas. We have studied the cellular composition of normal non-reactive and of regional drain- ing lymph nodes of colon and gastric adenocarcinomas. In normal non-reactive lymph nodes, T lymphocytes (CD2 + , CD7 + ) constituted the largest fraction of the lymphoreticu- lar cells. These lymphocytes were mainly CD4 + , and there were more cells expressing the CD45RA isoform of the CD45 antigen than CD45RO. Reactive lymph nodes pre- sented a decreased proportion of CD4 + CD45RA + cells and an increased number of B cells. Although most of the T cells in the reactive nodes were CD4 + CD45RO + , their propor- tion was similar to that found in normal non-reactive nodes. We studied the presence of the molecules CD28 and CD80 involved in the processes of interaction and activation of T and B lymphocytes. The CD28 molecule was found in all the T lymphocytes, while the CD80 molecule was weakly expressed on the B lymphocyte membrane. Key wordsmLymph node T Lymphocytes CD45 antigen Tumour immunology The cellular basis for the immune response to tumours is supported by studies of the tumour-infiltrating lymphocytes (TIL) and of those that occupy the lymph nodes draining the tumour area. TIL have a CD8 + phenotype and recognise the associated antigen or HLA class I molecules, having shown their effectiveness in cancer therapy [3, 4, 10, 11, 13, 14, 19, 20]. The immune response of the local lymph nodes is considered to be of little significance since there is no evidence that the said response impedes tumour develop- ment; in fact, these lymph nodes are the commonest sites for nesting and development of tumour metastases [6]. Moreover, there are data suggesting the existence of im- munosuppressive mechanisms within the local lymph nodes in the antitumour response, such as the decrease in re- sponses to mitogens exhibited by the lymphocytes of these lymph nodes and the positive results in immunosuppression tests [8, 9]. Despite these findings, there are no conclusive data concerning the characteristics of the response or its effectiveness. The most decisive evidence of the existence of an immune response in the lymph nodes that drain the tumour is their augmented size as a consequence of the increase in the number of lymphoid cells [6]. Few studies have been performed to assess the composition of the lymphocyte subpopulation within the lymph nodes, and these studies have failed to compare control nodes with non-reactive ones [7, 12, 16]. In this report, we describe the changes taking place in the lymph nodes reactive to gastric tumours and to colon adenocarcinomas, comparing them with nor- mal, non-reactive lymph nodes (cystic nodes). The results demonstrate an increase in the proportion of B lymphocytes and a reduction in the CD4 + T lymphocytes that express the CD45RA isoform of the CD45 antigen in lymph nodes that are reactive to gastric and colon adenocarcinomas. Patients and lymph nodes The study population comprised patients (32 – 78 years) with gastric (12 cases) or colorectal cancer (18 cases). Enlarged regional lymph Supported by grant 93/0955 from Fondo de Investigaciones Sanitarias de la Seguridad Social B. Lores-Vazquez M. Pacheco-Carracedo F. Gambo ´n-Deza ( ) Unidad de Inmunologia, Hospital do Meixoeiro, Apdo.s/n. 36200 Vigo, Spain J. Oliver-Morales Servicio de Anatomı ´a Patolo ´gica, Hospital do Meixoeiro, Vigo, Spain P. Parada-Gonzalez Servicio de Cirugia General, Hospital do Meixoeiro, Vigo, Spain Cancer Immunol Immunother (1996) 42: 339 – 342  Springer-Verlag 1996