Follicular lymphoma (FL) is the second most common non-Hodgkin’s lymphoma. In this work, comparative analysis was carried out of transcriptomes of tumor tissue samples from patients with FL in comparison with control samples of lymph nodes with reactive follicular hyperplasia in order to search for intracellular signaling pathways of the immune response, the functioning of which is altered in the tumor and its microenvironment. Nine hundred and ninety-seven genes were found, the expression of which differs in tumor and control samples. Of these, 430 genes are overexpressed in FL, while 567 genes exhibit decreased expression. Signaling pathways for the regulation of the cell cycle, cell response to stress and DNA damage, chromosome organization, and RNA processing have been activated. Among genes with reduced expression, genes associated with signaling pathways that control the immune response predominate. One of the most suppressed signaling pathways in FL controls the activation of T-lymphocytes. Of the 29 genes involved in the activation of T cells, the expression of which is suppressed in FL, three genes (CD28, LAT, and ZAP70) are involved in signal transduction in anti-PD-1 therapy. Thus, the level of expression of these genes in a patient can potentially be a biomarker of predictive value in anti-PD-1 therapy in FL.