Preferential production and secretion of the complement regulator factor H-like protein 1 (FHL-1) by human myeloid cells.

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 extrahepatic production of complement 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.

Properdin produced by dendritic cells contributes to the activation of T cells.

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 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.

Initial properdin binding contributes to alternative pathway activation at the surface of viable and necrotic cells.

Properdin, the only known positive regulator of the complement system, stabilizes the C3 convertase, thereby increasing its half-life. In contrast to most other complement factors, properdin is mainly produced extrahepatically by myeloid cells. Recent data suggest a role for properdin as a pattern recognition molecule.

Culture medium used during small interfering RNA (siRNA) transfection determines the maturation status of dendritic cells.

Gene silencing using small interfering ribonucleic acids (siRNA) is a powerful method to interfere with gene expression, allowing for the functional exploration of specific genes. siRNA interference can be applied in both cell lines, as well as in primary, non-dividing cell types like dendritic cells. However, the efficacy in different cell types is variable and requires optimization.

Identification of a novel non-coding mutation in C1qB in a Dutch child with C1q deficiency associated with recurrent infections.

Introduction: C1q deficiency is a rare genetic disorder that is strongly associated with development of systemic lupus erythematosus (SLE). Several mutations in the coding regions of the C1q genes have been described that result in stop-codons or other genetic abnormalities ultimately leading to C1q deficiency. Here we report on a Dutch boy suffering from recurrent infections with a complete C1q deficiency, without any SLE symptoms.