Characterisation of tumour infiltrating lymphocytes and correlations with immunological surface molecules in colorectal cancer

Using flow cytometry, we studied the phenotype of tumour infiltrating lymphocytes (TILs) in 41 enzymatically dissociated colorectal cancers and compared this to the expression of HLA class I and II and CD80 on tumour cells. We studied the possible enzymatic damage to various surface markers after enzymatic dissociation. The reproducibility of flow cytometric determinations obtained from TILs was good (kappa value: 0.79). The median CD4 +/CD8 + ratio was 2.2. Approximately 43–45% (median of cells in each tumour) of both the CD4 +- and the CD8 +-TILs expressed HLA class II; 14.2% of the CD4 +-TILs expressed CD25 and none of the CD8 +-TILs expressed CD25. CD3 −/CD16 +/CD56 +-TILs were very infrequent. Expression of HLA class II did not correlate with any lymphocyte surface markers. Since TILs are “turned off” rather than stimulated when tumour cells express HLA class II but not CD80, the lack of correlations could be due to anergy.