Scientists, including those of Indian origin, have identified new types of blood cells in the human immune system. The cells are new classes of types of white blood cells called dendritic cells and monocytes, researchers said.Researchers, including Rahul Satija from New York University and Karthik Shekhar from Broad Institute of MIT and Harvard in the US, identified two new dendritic cell subtypes and two monocyte subtypes. They have also discovered a new dendritic cell progenitor.

     Researchers used a technique called single-cell genomics to analyse gene expression patterns in individual human blood cells. Previously, different types of immune cells were investigated and defined by the set of marker proteins that they express on their surface.This new technique is much more powerful and can reveal previously unrecognised and rare cell types that would be otherwise difficult to find. Dendritic cells display molecules called antigens on their surfaces. These molecules are recognised by T cells which then mount an immune response. Monocytes are the largest type of white blood cell and can develop into macrophages that digest debris in our cells.

     “Two important white blood cell types in our bodies help defend us from infection - dendritic cells and monocytes,” said Divya Shah, from Wellcome Trust’s Infection and Immunobiology team. “In this study, scientists have used cutting-edge technologies to find that there are many more types of cell than we originally thought.“The next step is to find out what each of these cell types do in our immune system, both when we’re healthy and during disease,” said Shah. The finding was published in the journal Science.