Researchers have discovered new cell subtypes in the human immune system. The newly-discovered cells — dubbed monocytes and dendritic — fall under the white blood cell class. Thus, technically scientists have found new blood cells in the human body.

Human blood contains many types of cells, including components of our immune system. Primarily, there are three types of cells in the blood — red blood cell or RBC, white blood cell or WBC, and platelets.

Along with the discovery of the subtypes, the researchers also found a new progenitor of dendritic cell. Wellcome organization has funded the study and this discovery is one of the first major findings of the organization's Human Cell Atlas project.

What Are Dendritic Cells And Monocytes?

Dendritic cells or DCs contain molecules known as antigens on its surface. These molecules are identified courtesy the T cells, which trigger an immune response in human body.

Monocytes, on the other hand, are the largest WBCs present in human blood. These cells can grow into macrophages, which digest the debris in human cells.

DCs along with monocytes contain a number of specialized subtypes, which play a major role in antigen presentation, pathogen sensing, and phagocytosis.

However, understanding of these cells and their interrelationships are still vague. Historically, a combination of physical properties, functions, morphology, localization, developmental origins, and a restricted set of surface markers have defined these populations.

New Cells Discovered In Human Blood: How Did Researchers Find Them?

Earlier, a diverse set of immune cells were studied and defined according to a set of surface marker proteins. However, for this new experiment, researchers resorted to a technique known as single-cell genomics to observe and analyze "expression patterns in individual human blood cells."

To discover the blood subtypes, researchers performed single-cell RNA sequencing of approximately 2,400 cells. These cells were extracted from blood taken from healthy donors.

"This single-cell profiling strategy and unbiased genomic classification, together with follow-up profiling and functional and phenotypic characterization of prospectively isolated subsets, led us to identify and validate six DC subtypes and four monocyte subtypes, and thus revise the taxonomy of these cells," stated the researchers.

Results Of the Study

Other than discovering the subtypes and progenitors in human blood cells, the researchers believe that this study has given them in-depth understanding of the functions of monocytes and dendritic cells.

"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," stated Divya Shah, a researcher from Wellcome's Infection and Immunobiology team.

The scientists believe that this new method of classification of immune cells will not only help researchers analyze the cells accurately, in terms of functionality and development, but also help monitor the human body's immune system at all times.

The findings of the study have been published in journal Science on Friday, April 21.

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