Natural Killer T cell subsets in eutopic and ectopic endometrium: a fresh look to a busy corner

PURPOSE: Invariant Natural Killer T cells (iNKT) are a specialized subset of T cells that use their T cell receptor to recognize self and foreign lipids presented by CD1d as cognate antigens. iNKT have been shown to have either protective or harmful roles in many pathological states, including microbial infection, autoimmune disease, allergic disease and cancer. Accumulating evidence seems to suggest that this unique T cell subset combines both classically innate and adaptive immunologic characteristic. Considering these recent data, the aim of work was to review the current knowledge about iNKT in eutopic and ectopic endometrium. METHODS: Narrative overview, synthesizing the findings of literature retrieved from searches of computerized databases. RESULTS: Currently, the immune paradigm of reproduction is gradually changing shape: recent data confirmed that cytokine milieu influences the development and plasticity of different subtype of mononuclear cells, and in turn it can be influenced by the cytokine production of the latter. Among the different NKT cell populations, the recently characterized iNKT seems to share actions typical both of innate and adaptive immunity, being capable of secreting Th1 as well as Th2 cytokine pattern. Moreover, several subtypes of iNKT were identified, who partially express the same master transcription factors of the corresponding T cells counterpart. CONCLUSIONS: Although the data about iNKT's actions in eutopic and ectopic endometrium are still scarce, it is possible to hypothesize that future investigation can shed light on this point, thus allowing a better knowledge about the regulation of these two microenvironments.