Factor H is a pivotal complement regulatory protein that is preferentially produced by the liver and circulates in high concentrations in serum. There has been an increasing interest in the... Show moreFactor H is a pivotal complement regulatory protein that is preferentially produced by the liver and circulates in high concentrations in serum. There has been an increasing interest in the extrahepatic production of comple-ment factors, including by cells of the immune system, since this contributes to non-canonical functions of local complement activation and regulation. Here we investigated the production and regulation of factor H and its splice variant factor H-like protein 1 (FHL-1) by human myeloid cells. As validation, we confirmed the pre -dominant presence of intact factor H in serum, despite a strong but comparable mRNA expression of CFH and FHL1 in liver. Comparable levels of CFH and FHL1 were also observed in renal tissue, although a dominant staining for FHL-1 was shown within the proximal tubules. Human in vitro generated pro-and anti-inflammatory macrophages both expressed and produced factor H/FHL-1, but this was strongest in pro-inflammatory macro-phages. Production was not affected by LPS activation, but was increased upon stimulation with IFN-gamma or CD40L. Importantly, in both macrophage subsets mRNA expression of FHL1 was significantly higher than CFH. More -over, production of FHL-1 protein could be confirmed using precipitation and immunoblotting of culture su-pernatants. These data identify macrophages as producers of factor H and FHL-1, thereby potentially contributing to local complement regulation at sites of inflammation. Show less
Alem, C.M.A. van; Bank, J.R.; Vries, D.K. de; Bajema, I.M.; Mallat, M.J.K.; Fijter, J.W. de; ... ; Kooten, C. van 2022
Acute cellular rejection (ACR) occurs in 10% of renal allograft recipients and is characterized by leukocyte infiltration as observed in needle biopsies. ACR onset is subject to several risk... Show moreAcute cellular rejection (ACR) occurs in 10% of renal allograft recipients and is characterized by leukocyte infiltration as observed in needle biopsies. ACR onset is subject to several risk factors, including delayed graft function (DGF). As the impact of DGF on the etiology of ACR remains unclear, this study analyzed the association between presence of leukocyte subsets and ACR onset, in DCD kidney biopsies with extensive DGF following transplantation. Immunohistochemical analysis of protocol biopsies taken 10 days after kidney transplantation revealed that patients with high levels of renal CD163+ macrophages have a decreased risk (OR = 0.021, P = 0.008) for ACR in the first 6 months after transplantation. In pre-transplant biopsies of a comparable DCD cohort, with >80% DGF, presence of donor CD163+ macrophages showed no effect on ACR risk. Therefore, leukocyte infiltrate present during the inflammatory response at the time of DGF may contain anti-inflammatory macrophages that exert a protective effect against ACR development. Show less
Essen, M.F. van; Schlagwein, N.; Gijlswijk-Janssen, D.J. van; Ruben, J.M.; Kooten, C. van; COMBAT Consortium 2022
The complement system does not only play an important role in the defence against microorganism and pathogens, but also contributes to the regulation of innate and adaptive immunity. Especially... Show moreThe complement system does not only play an important role in the defence against microorganism and pathogens, but also contributes to the regulation of innate and adaptive immunity. Especially activation fragments C3a and C5a and complement activation at the interface of antigen presenting cell (APC) and T cell, were shown to have a role in T cell activation and proliferation. Whereas most complement factors are produced by the liver, properdin, a positive regulator of the C3 convertase, is mainly produced by myeloid cells. Here we show that properdin can be detected in myeloid cell infiltrate during human renal allograft rejection. In vitro, properdin is produced and secreted by human immature dendritic cells (iDCs), which is further increased by CD40-L-matured DCs (mDCs). Transfection with a specific properdin siRNA reduced properdin secretion by iDCs and mDCs, without affecting the expression of co-stimulatory markers CD80 and CD86. Co-culture of properdin siRNA-transfected iDCs and mDCs with human allogeneic T cells resulted in reduced T cell proliferation, especially under lower DC-T cell ratio's (1:30 and 1:90 ratio). In addition, T cell cytokines were altered, including a reduced TNF-alpha and IL-17 secretion by T cells co-cultured with properdin siRNA-transfected iDCs. Taken together, these results indicate a local role for properdin during the interaction of DCs and allogeneic T cells, contributing to the shaping of T cell proliferation and activation. Show less
Xu, W.; Zhao, X.W.; Daha, M.R.; Kooten, C. van 2013
