Genotype-phenotype correlations of low-frequency variants in the complement system in renal disease and age-related macular degeneration.

Genetic alterations in the complement system have been linked to a variety of diseases, including atypical hemolytic uremic syndrome (aHUS), C3 glomerulopathy (C3G), and age-related macular degeneration (AMD). We performed sequence analysis of the complement genes complement factor H (CFH), complement factor I (CFI), and complement C3 (C3) in 866 aHUS/C3G and 697 AMD patients. In total, we identified 505 low-frequency alleles, representing 121 unique variants, of which 51 are novel. CFH contained the largest number of unique low-frequency variants (n = 64; 53%), followed by C3 (n = 32; 26%) and CFI (n = 25; 21%). A substantial number of variants were found in both patients groups (n = 48; 40%), while 41 (34%) variants were found only in aHUS/C3G and 32 (26%) variants were AMD specific. Genotype-phenotype correlations between the disease groups identified a higher frequency of protein altering alleles in short consensus repeat 20 (SCR20) of factor H (FH), and in the serine protease domain of factor I (FI) in aHUS/C3G patients. In AMD, a higher frequency of protein-altering alleles was observed in SCR3, SCR5, and SCR7 of FH, the SRCR domain of FI, and in the MG3 domain of C3. In conclusion, we observed a substantial overlap of variants between aHUS/C3G and AMD; however, there is a distinct clustering of variants within specific domains.

Neuronal chemokines: versatile messengers in central nervous system cell interaction.

Whereas chemokines are well known for their ability to induce cell migration, only recently it became evident that chemokines also control a variety of other cell functions and are versatile messengers in the interaction between a diversity of cell types. In the central nervous system (CNS), chemokines are generally found under both physiological and pathological conditions. Whereas many reports describe chemokine expression in astrocytes and microglia and their role in the migration of leukocytes into the CNS, only few studies describe chemokine expression in neurons. Nevertheless, the expression of neuronal chemokines and the corresponding chemokine receptors in CNS cells under physiological and pathological conditions indicates that neuronal chemokines contribute to CNS cell interaction. In this study, we review recent studies describing neuronal chemokine expression and discuss potential roles of neuronal chemokines in neuron-astrocyte, neuron-microglia, and neuron-neuron interaction.

Chemokine scavenging by the human cytomegalovirus chemokine decoy receptor US28 does not inhibit monocyte adherence to activated endothelium.

The human cytomegalovirus has found smart ways to exploit the chemokine network in order to subvert immune attack. Chemokines trigger the arrest and firm adhesion of inflammatory cells to the vascular wall. Scavenging of chemokines by viral decoy receptors, such as US28, might prevent arrest of leukocytes to the vascular wall and impair an antiviral immune response. We determined the effect of chemokine scavenging by endothelium-expressed signaling mute US28 (US28R129A) on static monocyte adhesion. Despite the chemokine scavenging capacity of US28R129A, expression of this construct by endothelial cells was insufficient to disrupt leukocyte adhesion to cytokine-activated monolayers. Our results suggest that the concentrations of chemokines that trigger firm leukocyte adhesion are too high to be efficiently scavenged by viral chemokine decoy receptors like US28. From the results of this experimental model a role for US28 in viral immune evasion by chemokine scavenging would appear therefore unlikely.