Mononuclear inflammatory cells (MIC) are immune cells with a single, large, round nucleus. They are involved in immune responses and are found in peripheral blood mononuclear cells. MICs accumulate at the site of inflammation and consist of various cell types, including both stem cells and mature and immature cells from myeloid, erythroid, and lymphoid lineages. MIC recognises various antigens via pattern-recognition receptors TLRs as well as scavenger receptor C-type lectins. Key types of MICs include monocytes, lymphocytes, macrophages, and plasma cells.
-
Monocytes: These cells are precursors to dendritic cells and macrophages. They circulate in the bloodstream and are recruited to tissues, where they differentiate into macrophages and act as phagocytes.
-
Lymphocytes: This group includes T cells, B cells, and natural killer (NK) cells, which are essential in adaptive immunity and regulating immune responses.
-
Macrophages: These are differentiated monocytes responsible for phagocytosis. They are actively recruited to sites of infection, where they engulf and remove pathogens or dead cells.
-
Plasma cells: Differentiated B cells responsible for producing antibodies, plasma cells play a crucial role in the immune response.
MICs play distinct roles in different types of inflammation:
-
Acute inflammation: Neutrophils are the first responders to acute inflammation. Macrophages then arrive to help clear debris and initiate the healing process.
-
Chronic inflammation: The combined involvement of macrophages and lymphocytes in chronic inflammation can result in tissue damage and scarring.
-
Tumorigenesis: Chronic inflammation driven by MICs can lead to excessive DNA damage, increasing the risk of cancer development. An example of this is Inflammatory Bowel Disease (IBD).