A new study reveals that the immune cells that infiltrate metastatic melanoma are activated by the microenvironment of the tumor cells.
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Results of his study showed an alternative path whereby naive lymphocytes were activated locally in the tumor microenvironment. "Fundamental knowledge like this is crucial as we seek to understand how tumors escape antitumor immune responses and how we can develop approaches to counter this," he said.
For the majority of immune responses mounted by our bodies, for example in response to invading microbes, the predominant sites of lymphocyte activation are the lymph nodes, spleen and mucosal-associated lymphoid tissues. All these sites are dedicated to supporting the initiation and maintenance of immune responses. However, in some instances of chronic infection, for example with hepatitis C virus, ectopic lymphoid structures, or lymphoid structures that resemble lymph nodes and develop at aberrant locations, form at the site of the infection and locally support lymphocyte responses directed against the infectious agent.
Ectopic lymphoid structures have also been observed in some malignant tumors, including breast, lung and colorectal tumors, but not melanoma. In some studies, their presence has been linked to improved prognosis.
Van Baren and colleagues observed ectopic lymphoid structures in seven out of 29 skin metastases from patients with melanoma. In contrast, no primary melanoma samples examined contained complete ectopic lymphoid structures. However, some of them hosted small blood vessels that are associated with these structures.
Further analyses indicated that the ectopic lymphoid structures were functional, as features indicative of activation of the B cell lymphocyte subset were observed.
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The sample size was too small to allow the researchers to draw clinically meaningful conclusions. "Nonetheless, it will be important to look at this moving forward, as it is not yet clear whether these structures are good for the patient and bad for the tumor or good for the tumor and bad for the patient. At this point, there is no indication either way, and we could provide a speculative argument for either."
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Source-Eurekalert