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Infections are a major cause of childhood mortality. We investigated components of the lectin pathway of complement activation in the context of sepsis at both genetic and protein levels in neonates, infants and older children. Major components of the lectin pathway and two genes for Toll-like receptors were studied in 87 neonates with confirmed sepsis and compared with 40 babies with infections who did not develop sepsis (disease controls) and 273 infection-free neonatal controls. A second cohort comprised 47 older children with sepsis and 87 controls. Low MBL-conferring genotypes (LXA/O+O/O) were more frequent in sepsis patients than in healthy controls but no significant differences in the frequency of SNPs of other lectin pathway genes (FCN1, FCN2, FCN3, MASP1/3, MASP2) or TLR receptor genes (TLR2, TLR4) were found. One case of primary MASP-2 deficiency was found among healthy pre-terms and one neonate suffering from SIRS was heterozygous for the rare FCN1 gene mutation, +6658 G>A. Generally, sepsis was associated with low serum MBL and low ficolin-2 concentrations on admission. Among neonates, ficolin-1 and MASP-2 levels were elevated in sepsis relative to healthy, but not disease, controls. Unlike neonates, ficolin-3 and MASP-2 levels were lower in older patients than in healthy controls while no difference was found for ficolin-1. With the possible exception of MBL, inherited lectin pathway insufficiencies do not seem to predispose to sepsis, rather changes in protein concentrations reflect alterations in disease course.

We conducted a prospective study of 453 Polish patients suffering from pulmonary tuberculosis and 267 healthy controls. Selected polymorphisms of the genes encoding for collectins, ficolins and MBL-associated serine protease 2 were investigated as were serum concentrations of mannose-binding lectin, surfactant protein D, ficolin-1 and ficolin-3. The number of MBL2 gene exon 1 variant allele carriers was significantly higher in patients, compared with controls. The homozygosity for SFTPA2 +26 C > A SNP variant allele occurred less commonly within TB, while homozygosity for the FCN1 -542 G > A major allele was less frequent within the control group. Two patients were found MASP-2-deficient. Serum concentrations of MBL, SP-D and ficolin-1 were higher amongst patients while the converse was found for ficolin-3. Ficolin-1 had high specificity to differentiate between individuals with tuberculosis and healthy persons and therefore may be considered potential disease marker.

Background Ficolin-3 is a pattern-recognition molecule with the ability to activate the lectin pathway of complement. It is found in lung, liver and blood, but its physiological role is unclear. We have investigated interaction of recombinant ficolin-3 with malignant cells and tissues. Material and Methods Cells of various lines of human origin as well as ovarian tissue sections have been studied with the use of flow cytometry and immunohistochemistry. Results Recombinant (but not serum-derived) ficolin-3 was found to bind strongly to the ovarian cancer cell lines, SKOV-3, OVCAR-3 and ES-2, at concentrations of 2.5 μg/ml and above. Moreover, His-tagged recombinant ficolin-3 (10 μg/ml) preferentially stained ovarian tissue sections from patients with malignant tumours compared with those from patients without. Binding to cell lines was inhibited by EDTA and specific carbohydrate ligands, indicating involvement of the fibrinogen-like domain. Binding was enhanced under mildly acidic conditions and at physiological pH after pre-incubation of cells with mildly acidic buffer. Conclusion Basing on data concerning recombinant protein, it may be suggested that ficolin-3 is involved in immune response in ovarian cancer. However, unidentified serum factor(s) seem(s) to protect cancer cells from recognition by natural or rficolin-3.

Ficolin-3 (also called H-ficolin or Hakata antigen) is a complement-activating pattern recognition molecule, possessing a fibrinogen-like domain involved in carbohydrate binding. Amongst human ficolins, Ficolin-3 has the highest concentration in serum and is the most potent lectin pathway activator in vitro. Evidence for its physiological function is sparse, although its deficiency has been suggested to increase susceptibility to infections. The specificity of Ficolin-3 is poorly characterized and currently few ligands are known. Here we report agglutination of Hafnia alvei, a Gram-negative enteric commensal bacterium and opportunist pathogen, in the presence of recombinant Ficolin-3 and calcium. Ficolin-3 also augmented phagocytosis of H. alvei by macrophages and displayed bactericidal activity. Additionally, Ficolin-3 inhibited host cells’ response to TLR4/MD-2/CD14-LPS dependent NF-κB activation. This is the first demonstration of protective activity of Ficolin-3 against a human bacterial pathogen. Although human Ficolin-3 does not recognise and bind to common pathogenic bacteria, it could be an important component of innate immunity providing protection, for example, from commensal flora that can cause extraintestinal, opportunistic infections.

Inflammatory bowel disease (IBD) refers to disorders associated with progressive inflammatory processes in the gastrointestinal system. IBD consists of two major forms, Crohn’s disease (CD), and ulcerative colitis (UC). IBD became a global disease in the 21st century. Its pathogenesis is still not fully understood. Mannose-binding lectin (MBL) is a pattern-recognising molecule, involved in anti-microbial and anti-cancer immunity. It is able to opsonize microorganisms and abnormal host cells, and to initiate complement activation. The aim of this study was to investigate possible involvement of MBL in inflammatory bowel disease in adults. Forty persons diagnosed with CD and 28 with ulcerative colitis were recruited. The control group consisted of 136 healthy persons. Single nucleotide polymorphisms of the MBL2 gene (localised to both promoter and exon 1) were determined as were serum MBL concentrations. The exon 1 variant alleles and MBL deficiency-associated genotypes were more frequent among patients compared with controls, although this difference was not statistically significant. No differences of MBL levels were found between the major groups. However in MBL2 A/A homozygous IBD patients, the median was significantly higher than in corresponding healthy subjects. That was particularly evident in the case of active Crohn’s disease (1493 ng/ml vs. 800 ng/ml, p = 0.021). It may suggest that MBL and MBL-dependent complement activation contributes to excessive inflammation and its adverse effects in the course of CD. It cannot also be excluded that high MBL activity constitutes in some cases part of a multifactorial network conducing to development of CD.

Ficolin-3 (also called H-ficolin or Hakata antigen) is the most potent activator of the lectin pathway of complement in vitro. Its genetically determined deficiency in Caucasians is associated with a frame-shift mutation +1637delC (rs28357092) of the FCN3 gene. When it was described for the first time, it was postulated to be strictly associated with enhanced susceptibility to infections. At present, with our knowledge extended by several other patients that issue seems to be more complicated and less clear-cut. Two new cases of primary Ficolin-3 deficiency are reported here: a 50-year old male, suffering from membranous nephropathy and an 11-month old male infant who was operated on to repair congenital heart disease. Based on those cases and a literature review, we conclude that the clinical consequences of congenital Ficolin-3 deficiency are still unclear and such questions as whether it may be life-threatening or acts as a disease modifier remain to be elucidated.

Serum H-ficolin (ficolin-3) concentrations (n=613) and FCN3 genotypes (n=529) from a large group of neonates are presented. Both pre-term deliveries and low birthweight (independently of gestational age) were significantly associated with low H-ficolin concentrations but not with heterozygosity for the FCN3 1637delC frameshift mutation. The presence of the variant allele, however, apparently influenced the protein level. No association of FCN3 gene heterozygosity or relative functional H-ficolin insufficiency (determined as serum level ≤8.6 μg/ml) with perinatal infections was found. One premature newborn, with confirmed infection caused by Streptococcus agalactiae, was H-ficolin-deficient (FCN3 variant homozygote, no detectable protein). We present what is only the fourth case report of total H-ficolin deficiency in the world literature. This neonate was however previously found to be mannan-binding lectin (MBL) as well as MBL-associated serine protease-2 (MASP-2) deficient and also had low serum L-ficolin.

We investigated MBL2 and MASP2 genotypes, serum MBL (mannose-binding lectin) levels and activities of its complexes with associated serine proteases (MASP-1, MASP -2), in relation to complications following cardiac surgery in 195 children. The incidence of SIRS was lower in patients carrying MBL2 A/O and O/O genotypes (p=0.024). Children with MBL levels500ng/ml had a lower risk of SIRS (p=0.014) and fever (p=0.044). Median MBL concentration was higher in patients who developed SIRS (p=0.048) but lower in those with post-operative infections (p=0.046). MBL-MASP-2 activities100mU/ml protected from SIRS (p=0.007), low cardiac output syndrome (p=0.03) and multiorgan failure (p=0.012). In contrast, MBL2 YA/YA genotypes were associated with SIRS (p=0.018), low cardiac output syndrome (p=0.018), fever (p=0.018) and high inotropic score (VIS30) (p=0.021). Thus, low MBL concentrations and associated genotypes may protect patients from systemic inflammation while high MBL serum levels and corresponding genotypes are risk factors of postoperative complications.