Background: IgA nephropathy (IgAN), also known as Berger’s nephropathy, is the most common form of glomerulonephritis worldwide. Often, the disease affects adults at ages of 20 to 30 years, and the disease occurs almost twice as often in males as in females. The etiology of IgAN is to date unknown, but it is clear that poorly galactosylated immunoglobulin IgA1 is the trigger in the development of nephritis. The complex pathogenesis of IgAN has been studied in attempt to unravel key abnormalities of this disease, and over the past two decades significant progress has been made. However, incomplete understanding of the origins of IgA1 molecules, the formation of circulating immune complexes, and of the cellular events of inflammation, has affected the development of specific therapeutic strategies of IgAN. Therefore, management of patients has been with generic therapies, mainly in attempt to control blood pressure. Confusion over correct and optimal treatment remains, and there is a need for studies investigating cellular events of IgAN to be able to develop specific therapies in the future.

Materials and Methods: Flow cytometric enumeration was made on monocyte and dendritic cell subpopulations in anti-coagulated whole blood from IgAN patients and in healthy individuals. Also, the presence of monocytes in urine from IgAN patients and healthy control subjects was investigated by flow cytometry. TLR4 and HLA-DR expression of monocyte and dendritic cell subpopulations was determined.

Results: Enumeration of dendritic cell and monocyte subpopulations in IgAN patients and in healthy controls succeeded. In all subjects the subpopulations of cells were found. The monocyte and dendritic cell subpopulations being investigated in the present study have only recently been defined (3), and to our knowledge, the distribution of subpopulations within parent population of these cells in blood has not yet been investigated in IgAN. Urine monocytes were found in one patient but not in control subjects. HLA-DR expression of dendritic cell subpopulations seemed to be consistent between all subjects with highest peak values of median fluorescence intensity seen in samples from control subjects. Intermediate monocytes expressed most HLA-DR in comparison with classical and non-classical monocytes. The intermediate monocytes of control subjects expressed more HLA-DR than intermediate monocytes of IgAN patients.

Conclusion: By this study it was confirmed, that multicolor flow cytometry offers the opportunity of analysis of intermediate, non-classical, and classical monocytes, as well as plasmacytoid CD303+, myeloid CD1c+, and myeloid CD141+ dendritic cells in IgAN patients. Multicolor flow cytometry provides the capability of detection of multiple colors. However, reflections should be made in order to obtain useful and high quality data. In this study, it has been clearly shown, that the choice of fluorochrome-conjugated antibodies of the experimental antibody panel should be considered carefully, particularly when using fluorochromes that may show a high degree of non-specific binding to cells. It was emphasized, that there is a need for careful quality controls when using tandem-conjugated antibodies. The number of patients and control subjects for this type of experiment should be increased in a future study, as this would provide better opportunities for evaluation of cellular events in IgAN and in health. By also implementing various improvements of the flow cytometric measurements, great opportunities would arise to achieve more information on the condition of the innate immune system in IgAN.