Immune responses occurred locally in melanoma metastases
The presence of lymphoid neogenesis in melanoma metastases suggested that functional ectopic lymphoid structures, directly contacting tumors, made local development of antimelanoma cell response achievable in a recent study.
Investigators in Belgium collected 29 tumor samples from patients with metastasized melanoma. In seven samples, complete ectopic lymphoid structures — defined as lymphoid follicles that included clusters of B lymphocytes surrounding follicular dendritic cells — were detected and associated with T cell clusters and high endothelial venules (HEV). Unlike metastatic lesions, primary melanomas did not host follicles, but many contained HEV, indicating the possibility of incomplete lymphoid neogenesis.
After analyzing rearranged immunoglobulin genes in B cells of microdissected follicles, researchers noted clonal amplification, somatic mutation, and isotype switching. They said this emphasized a local antigen-driven B-cell response, while IgA response also was observed despite nonmucosal location of the follicles.
“We report here for the first time the presence of ectopic lymphoid structures in human melanoma metastases,” the researchers concluded, noting the study’s small sampling. “Our observations do not allow [us] to determine whether these local immune responses are directed at melanoma antigens, but we feel that this is a realistic possibility. To assess whether lymphoid neogenesis helps or impairs tumor progression, it will be important to evaluate its prognostic impact in a large series of melanoma patients.”