CD85k Contributes to Regulatory T Cell Function in Chronic Viral Infections

Adaptive and Innate Cytotoxic Effectors in Chronic Lymphocytic Leukaemia (CLL) Subjects with Stable Disease

Chronic lymphocytic leukaemia (CLL) is characterised by the expansion of a neoplastic mature B cell clone. CLL clinical outcome is very heterogeneous, with some subjects never requiring therapy and some showing an aggressive disease. Genetic and epigenetic alterations and pro-inflammatory microenvironment influence CLL progression and prognosis. The involvement of immune-mediated mechanisms in CLL control needs to be investigated. We analyse the activation profile of innate and adaptive cytotoxic immune effectors in a cohort of 26 CLL patients with stable disease, as key elements for immune-mediated control of cancer progression. We observed an increase in CD54 expression and interferon (IFN)-γ production by cytotoxic T cells (CTL). CTL ability to recognise tumour-targets depends on human leukocyte antigens (HLA)-class I expression. We observed a decreased expression of HLA-A and HLA-BC on B cells of CLL subjects, associated with a significant reduction in intracellular calnexin that is relevant for HLA surface expression. Natural killer (NK) cells and CTL from CLL subjects show an increased expression of the activating receptor KIR2DS2 and a reduction of 3DL1 and NKG2A inhibiting molecules. Therefore, an activation profile characterises CTL and NK cells of CLL subjects with stable disease. This profile is conceivable with the functional involvement of cytotoxic effectors in CLL control.

Dampening antiviral immunity can protect the host

Viral infections are very common, and in most cases, the virus is well controlled and eliminated by the immune system. Nevertheless, in some cases, damage of the host tissue inflicted by the virus itself or by the elicited immune response may result in severe disease courses. Thus, regulatory mechanisms are necessary to control virus‐induced and immune pathology. This ensures immune responses are elicited in a potent but controlled manner. In this review, we will outline how immune regulation may contribute to this process. We focus on regulatory T cells and co‐inhibitory receptors and outline how these two regulatory immune components allow for and may even promote potent but not pathologic immune responses. By enabling a balanced immune response, regulatory mechanisms can thus contribute to pathogen control as well as tissue and host protection.