Abstract
"Monocytes are a vital component of the innate immune system. They are found circulating in the blood and play key roles in health and disease. In this thesis, I characterise monocytes using lineage determining cytokine receptors (LDCRs). LDCRs are pleiotropic cytokines which drive development, proliferation and maturation of leukocytes. Our knowledge of this cytokine receptor system in monocytes is fragmented.
I hypothesise that characterisation of Human monocytes with LDCRs could highlight the inter-relationship and ontogeny of populations defined by current phenotyping methods, provide new methods to separate cells, as well as help elucidate their origin and relationship to other circulating myeloid cells, such as dendritic cells.
I found the LDCR CSF1R to be a useful and overlooked Human pan-monocyte marker. With anti-CSF1R antibodies I was able to isolate all conventional monocytes by fluorescent cell sorting and magnetic isolation, in a method which we patented and are in the process of licensing. This cannot be done with the current monocyte markers of CD14 and CD16. This work further highlighted a population of CSF1R+ CD14- CD16- dendritic cells suggesting a close link to monocytes.
Multi-dimensional analysis of CSF1R+ cells with single cell RNA sequence and flow cytometry data highlighted a new monocyte delineation based on the LDCRs CSF2R and CSF3R. These represent an improved alternative to the conventional CD14 and CD16 delineation. Our new system outperforms CD14 and CD16 in colorectal cancer samples, where I discovered that the monocyte distribution defined by CSF2R and CSF3R was altered compared to control samples. Further diverse CSF2R and CSF3R distributions were identified in in vitro stimulated monocytes.
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I conclude that using the lineage cytokine receptors CSF1R, CSF2R, and CSF3R as monocytes markers could enable more accurate identification, quantification and isolation of monocytes and related cells in blood and offer a fresh perspective on monocyte heterogeneity."