Differentiating cells from one another is a crucial process in biomedical research. Determining the types of cells present in a sample can tell you a great deal about the health of that individual. Cell identity can be determined by the molecules present on their surface. In recent decades, an ever-expanding bank of these surface proteins, referred to as Cluster of Differentiation (CD) Proteins, have been collated and allow for reference when you take a sample. These proteins are not merely passive markers as the vast majority tend to have active functions in the functions of that particular cell.
CD determination is a useful tool in determining populations of cells in the blood, whose CD profile are indicative of specific populations, and hence for disease monitoring for cancers such as leukaemia. Blood samples taken at different points can give you an indication of the progress of disease, for example whether the patient is entering remission or if the cancer is proving stubborn to chemotherapy.
For example, the presence of both CD19 and CD10, in conjunction with additional surface markers, indicates a specific type of B cell, the cells that go on to produce antibodies when the immune system is stimulated by a foreign substance. Since some leukaemias, such as Acute Lymphoblastic Leukaemia (ALL), may arise from these cells, the detection of a larger-than-normal population of these cells is a concerning sign and can be used to track disease progression. Over time, if that population of cells begins to drop, it is clear that the chemotherapy being used is having an effect.
Using these markers, we can also increase our understanding of how all the cells in our blood differentiate and look through the hierarchy of all the progeny cells, all the way back to the stem cells at its very apex. We can use CD molecules to identify the stem cells themselves and enhance our understanding about stem cell biology – their function in physiological and pathological scenarios, how they go on to generate entire tissues and their role in regenerative medicine.
The identification of markers that identify specific populations of cells, and the technology to detect and separate such populations, has been one of the most important advances in medical biology in the last few decades. Both our understanding of cell biology and our ability to apply this at a clinical level has benefited immeasurably.
‘Til next time…