Fundamentals of immunology for understanding immunotherapy for lymphoma.

An effective antitumor immune response in patients with lymphoma would eradicate the malignant B cells and cure the patient of the disease. This, however, does not occur, and a suboptimal antitumor response results in persistence and subsequent progression of the patient's disease. The goals of immunotherapy are therefore to restore an effective antitumor immune response by promoting immune recognition, optimizing immune activation, and supporting persistence of the immune response resulting in subsequent immunological memory. Multiple mechanisms, however, are present within the tumor microenvironment that account for an inadequate immune response. These include loss of major histocompatibility complex expression on tumor cells and subsequent inadequate antigen presentation, increased expression of immunosuppressive ligands on malignant cells, populations of immune cells with suppressive function present in the tumor, and cytokines secreted by the malignant cell or other cells in the microenvironment that promote immune exhaustion or suppress the immune response. Successful immunotherapeutic strategies are specifically addressing these issues by promoting antigen presentation, improving recognition of the malignant cell, directly activating T cells and natural killer cells, and blocking immune checkpoint signaling that would suppress the immune response. Many of these approaches have proven highly successful in patients with various subtypes of lymphoma and are now being incorporated into standard clinical practice.