Can ficolin-2 (L-ficolin) insufficiency be established by a single serum protein measurement?

Serum ficolin-2 was measured in multiple (2-27) samples from 68 paediatric sepsis patients. Fourteen individuals (21%) gave values that included a change in status from 'normal' to 'insufficient' or vice versa. Therefore, if possible, ficolin-2 concentration should be determined in samples obtained when a disease is inactive.

Drug modification of LPS-stimulated human monocyte-derived dendritic cells.

Many drugs have been reported to convert dendritic cells (DCs) into a tolerogenic phenotype in vitro. However, there is evidence that an additional stimulus, such as lipopolysaccharide (LPS), may also be necessary for tolerogenic function in vivo. Little is known concerning the effects of drug modification on LPS-prestimulated DCs. In this study, monocyte-derived immature DCs were stimulated with LPS first and the influence investigated of six different agents on surface antigen expression, cytokine production and lymphocyte proliferation and cytotoxicity. Mycophenolic acid- and rapamycin-exposed DCs had little effect on surface antigen expression or functional activity towards lymphocytes. In contrast, treatment of immature dendritic cells with aspirin, dexamethasone, 1alpha,25-dihydroxyvitamin D3 (VD3) or butyric acid was associated with diminished expression of CD1a, CD1c, CD40, CD80 and CD83. Dendritic cell modification by aspirin, dexamethasone and VD3 were all associated with decreased production of tumour necrosis factor-alpha (TNFalpha). Furthermore, VD3 treatment was associated with a consistent and significant elevation of IL-6 production. Aspirin-, dexamethasone- VD3- and butyric acid-modified DCs suppressed interferon-gamma production, proliferation and cytotoxicity in co-culture with allogeneic mononuclear cells, but inconsistent results were obtained with different allogeneic combinations. Different drugs show varying effects on DC phenotype. No single agent was consistently effective in suppressing the stimulation of allogeneic mononuclear cells and future work is needed to explore drug combinations.

Extremes of L-ficolin concentration in children with recurrent infections are associated with single nucleotide polymorphisms in the FCN2 gene.

L-ficolin (also called ficolin-2, P35 or hucolin) is a soluble pattern recognition molecule of suspected importance in anti-microbial immunity. It activates the lectin pathway of complement and acts as an opsonin. l-ficolin, encoded by the FCN2 gene, recognizes microbial polysaccharides and glycoconjugates rich in GlcNAc or GalNAc. We report here data concerning four single nucleotide polymorphisms (SNPs) of the FCN2 gene and their relationship to l-ficolin serum concentrations. There are two pairs of SNPs in linkage disequilibrium: ss32469536 (located in promoter) with rs7851696 (in exon 8) and ss32469537 (promoter) with ss32469544 (exon 8). We selected groups possessing low or high serum l-ficolin concentrations (or= 4.5 microg/ml, respectively) from Polish children suffering from recurrent respiratory infections (n = 146). Low l-ficolin levels were associated with variant alleles for ss32469536 and rs7851696 and normal alleles for ss32469537 and ss32469544. Conversely, high l-ficolin levels were associated with variant alleles of ss32469537 and ss32469544. FCN2 genotyping should be a valuable additional tool for disease association studies.

Association between mannan-binding lectin and impaired lung function in cystic fibrosis may be age-dependent.

An association between mannan-binding lectin (MBL) status and severity of lung function impairment in cystic fibrosis (CF) has been found in several studies, but not in others. To explore the possible basis for discrepancies in the literature, we related both MBL and L-ficolin concentrations to lung function and examined the results in relation to the age of the patients. For patients under 15 years of age, those with MBL < 200 ng/ml had better lung function than those with MBL > 200 ng/ml [median forced expiratory volume in 1 s (FEV(1)), 99% versus 83%; P = 0.05]. For patients over 15 years of age, those with MBL < 200 ng/ml had poorer lung function than those with MBL > 200 ng/ml (median FEV(1), 44% versus 55%; P = 0.1). Also, for the over 15-year-olds, the proportion of patients with FEV(1) values below the median was greater in the MBL-insufficient subgroup (P < 0.04). In other words, relative deficiency of MBL appears to accelerate the age-related decline in lung function in CF patients. No corresponding relationships could be found between L-ficolin concentration and lung function. These findings and interpretation lend support to the potential value of MBL replacement therapy in a small minority of cystic fibrosis patients.

Human serum amyloid P component binds to peripheral blood monocytes.

The binding of human serum amyloid P component (SAP) to blood cells and monocyte-derived dendritic cells was investigated by flow cytometry. Monocytes bound biotinylated SAP with avidity in a dose-dependent and saturable manner. By contrast, the binding of SAP to monocyte-derived dendritic cells was weak. No binding to erythrocytes, NK cells, T lymphocytes or B lymphocytes could be detected. The SAP-monocyte interaction was calcium-independent and readily inhibited by C1q. SAP was nonmitogenic for human mononuclear cells and had no apparent influence on lymphocyte proliferation induced by mitogenic lectins. We speculate that binding of SAP by monocytes could be of physiological relevance at extravascular sites by influencing complement regulation.

Detection of an autologous ligand for mannan-binding lectin on human B lymphocytes.

Mannan-binding lectin (MBL) is a collectin and a major soluble pattern-recognition protein. MBL can distinguish self from nonself and altered self using its C-type carbohydrate recognition domain and may also interact via its collagen-like region with autologous cells. Recently, it was found that MBL could bind to adherent cells (monocytes) and dendritic cells in a specific and sugar-sensitive manner. We have now investigated the interaction of MBL with fresh human peripheral blood cells and report binding to B lymphocytes and natural killer cells. The binding to B lymphocytes was studied in detail and was compared with the binding of MBL to monocytes and dendritic cells. Binding of MBL to B cells was evident at physiological MBL and calcium concentrations but was optimal at supraphysiological MBL concentrations. It was readily inhibited by autologous serum, mannan, mannose, GlcNAc and (to a lesser extent) galactose but not by C1q. A similar, but not identical, inhibition profile was observed with dendritic cells, but monocytes were not sensitive to mannose or mannan. We conclude that MBL is capable of binding to differently glycosylated ligands on several autologous cell types via its carbohydrate-recognition domain. We speculate that this could have functional significance at extravascular sites, but perhaps only in individuals possessing MBL genotypes conferring MBL sufficiency.

Successful haemopoietic stem cell transplantation does not correct mannan-binding lectin deficiency.

It has been reported that in allogeneic stem cell transplantation, the mannan-binding lectin (MBL) status of the donor has prognostic value for the recipient. Two MBL-deficient patients, with coexisting haematological malignancy, were identified who were treated with bone marrow from donors with normal MBL concentrations. Although both patients engrafted successfully and remain in complete remission, neither seroconverted to the MBL sufficiency status of his donor over a follow-up period exceeding 2 years. This does not support the concept of MBL replacement by stem cell therapy, and does not provide an explanation for high MBL concentrations in stem cell donors protecting recipients from post transplant infections.

L-ficolin in children with recurrent respiratory infections.

The lectin pathway of complement activation is used by a collectin, mannan-binding lectin (MBL), and two ficolins, L-ficolin and H-ficolin, to opsonize microorganisms for phagocytosis. We published evidence recently that MBL insufficiency is associated with recurrent respiratory infections in childhood. We have now measured serum L-ficolin in 313 respiratory infection patients and 74 healthy control children. L-ficolin concentrations below the lower limit of the control group were found in 6% of the patients (P <0.02) and were associated most strongly with children having co-existing atopic disorders (11%; P=0.002). We suggest that L-ficolin may have a role in protection from microorganisms complicating allergic disease.

Mannan-binding lectin insufficiency in children with recurrent infections of the respiratory system.

Blood samples were collected over a 4-year period from 335 children (aged 1-16 years) suffering from recurrent respiratory infections and 78 controls. The patients were subdivided into four groups: I, children with no immune system defects detected (n = 101); II, children with allergies (n = 94); III, children with humoral response defects (n = 93); and IV, children with disturbances of cellular immunity (n = 66). Nineteen patients had both humoral and cellular abnormalities. All patients and controls were investigated to determine the exon 1 and promoter region variants of the mbl-2 gene. MBL serum concentrations were also determined in samples from 291 patients and 75 controls. The proportion of O (B, D or C) alleles was significantly higher in the patient group compared to controls, and this association was strongest for subgroup III. The promoter LX variant frequency was also commoner in the patients as a whole, and significantly so in subgroups II and IV. Genotypes markedly influenced MBL concentrations in all groups, and correlated with ability to activate the lectin pathway of complement activation. The strongest and most significant inverse correlations between serum MBL and respiratory disease were found in patient group III and in 17 patients with multiple humoral and/or cellular abnormalities. Among nine patients with unexpectedly low LP activity in view of their MBL concentrations, one person was found to be MASP-2 deficient. Our results indicate that mannan-binding lectin insufficiency, with or without a coexisting immune defect, is associated with the occurrence of recurrent respiratory infections in childhood, and this relationship is particularly strong and statistically significant in children with concomitant impairments of humoral immunity.

Comparison of adult and fetal cytokine secretion during mixed lymphocyte reactions.

Umbilical cord blood transplants are associated with a lower incidence of graft-versus-host disease (GVHD) than adult marrow or peripheral blood stem cell transplants, and this could be related to a difference in cytokine production between fetal and adult mononuclear cells after allogeneic stimulation. Mixed lymphocyte reactions (MLRs) involving adult cells were associated with greater interferon-gamma (IFNgamma) secretion than MLRs between cord blood cells, although IL-2 secretion was similar. Experiments in which T cells were separated from accessory cells then recombined in artificial combinations indicated that differences in T cells were primarily responsible for the greater [IFNgamma]:[IL-2] ratios generally found after MLRs involving adult cells compared to fetal cells, but accessory cells also influenced this ratio. The cellular basis for the observed difference was not established, but mononuclear cell preparations from cord blood contained significantly higher proportions of CD16(+)56(-) NK-type cells and a CD19(+)1c(+) B cell subset, as well as more CD45 RA-expressing nai;ve T cells.

No strong relationship between mannan binding lectin or plasma ficolins and chemotherapy-related infections.

Chemotherapy causes neutropenia and an increased susceptibility to infection. Recent reports indicate that mannan-binding lectin (MBL) insufficiency is associated with an increased duration of febrile neutropenia and incidence of serious infections following chemotherapy for haematological malignancies. We aimed to confirm or refute this finding and to extend the investigation to the plasma ficolins, P35 (L-ficolin) and the Hakata antigen (H-ficolin). MBL, L-ficolin and H-ficolin were measured in 128 patients with haematological malignancies treated by chemotherapy alone or combined with bone marrow transplantation. Protein concentrations were related to clinical data retrieved from medical records. MBL concentrations were elevated compared with healthy controls in patients who received chemotherapy, while L-ficolin concentrations were decreased and H-ficolin levels were unchanged. There was no correlation between MBL, L-ficolin or H-ficolin concentration and febrile neutropenia expressed as the proportion of neutropenic periods in which patients experienced fever, and there was no relation between abnormally low (deficiency) levels of MBL, L-ficolin or H-ficolin and febrile neutropenia so expressed. Patients with MBL < or =0.1 microg/ml had significantly more major infections than no infections within the follow-up period (P<0.05), but overall most patients had signs or symptoms of minor infections irrespective of MBL concentration. Neither L-ficolin nor H-ficolin deficiencies were associated with infections individually, in combination or in combination with MBL deficiency. MBL, L-ficolin and H-ficolin, independently or in combination, did not have a major influence on susceptibility to infection in these patients rendered neutropenic by chemotherapy. These results cast doubt on the potential value of MBL replacement therapy in this clinical context.

Introduction to mannan-binding lectin.

Mannan-binding lectin (MBL) was first discovered as a plasma opsonin for baker's yeast and was independently characterized biochemically. It belongs to the small subfamily of collectins: C-type lectins possessing a collagen-like domain. MBL is synthesized by the liver and secreted into the bloodstream. It is believed to be an important component of innate immunity, acting as an ante-antibody and/or as a disease modifier. It is thought to influence disorders as diverse as meningococcal disease, rheumatoid arthritis, cystic fibrosis and recurrent miscarriage. Lack of MBL may be most relevant in the context of a co-existing secondary immune deficiency. Replacement therapy, first carried out 30 years ago with unfractionated plasma, appears promising. The development of a recombinant product should permit the extension of MBL therapy to randomized clinical trials of sufficient size to provide clear evidence about the physiological significance of this intriguing glycoprotein.

Is there a relationship between HLA type and prognostic factors in breast cancer?

No convincing association exists between HLA type and breast cancer development but certain HLA types have been suggested to be associated with poor risk disease. Here, the HLA type (class I and II) for 141 breast cancer patients was compared to a control population of 100 individuals and to the prognostic indicators for the patients. No association was found between HLA type and breast cancer development. Consideration of individual HLA/prognostic factor relationships previously reported confirmed that HLA-B7 was over-represented in premenopausal oestrogen-receptor (ER)-positive, grade 3 tumours (p = 0.04) and that HLA-A1 correlated positively with Nottingham Prognostic Index (p < 0.05) and with ER-negative disease (p < 0.05). These findings suggest that some previously identified associations between HLA type I and particular prognostic factors may be real, if weak but appear to conflict with the only other sizeable study investigating HLA type II in breast cancer (which negatively correlated HLA-DR 11 with early onset disease).

Mannan-binding lectin and hepatitis C infection.

Japanese patients with chronic hepatitis C infection unresponsive to treatment with interferon possessed genotypes disproportionately conferring low mannan-binding lectin (MBL) concentrations. Our aims were to confirm or refute this finding in European patients at the MBL protein level, and to investigate whether a low circulating concentration of MBL might influence susceptibility to, or disease progression from, hepatitis C viral infection. Serum samples obtained from 180 hepatitis C patients and 566 blood donors were assayed for MBL. MBL concentrations were related to disease characteristics retrieved from patients' records. MBL concentrations were higher in hepatitis C patients (median 2.5 microg/ml versus 1.3; P < 0.0001) and the proportion of patients with very low (MBL-deficient) concentrations was similar to that of the healthy controls. There were no significant associations between patients with low serum MBL and the disease features studied, including response to antiviral therapy. Therefore, low circulating MBL does not increase susceptibility to hepatitis C infection, and MBL concentration does not have a major influence on the course of the disease or the response to antiviral therapy. MBL replacement therapy would therefore not be indicated for chronic hepatitis C patients who failed to respond fully to treatment with interferon and ribavirin.

Mannan-binding lectin and its role in innate immunity.

Mannan-binding lectin (MBL) is a plasma collectin (C-type lectin with a collagen-like domain) and is considered an important component of innate immunity. Circulating MBL is genetically determined for the major part, but plasma concentration is also markedly influenced by nongenetic factors. The carbohydrate-binding ability of MBL can be inhibited by simple sugars like mannose, fucose and N-acetylglucosamine, but its greatest avidity appears to be for repeating mannose-based structural patterns typical of microbial surfaces. By this means, MBL can bind to a wide variety of bacteria and other microbes, neutralizing them and/or opsonizing them by activating complement using the recently discovered lectin pathway of complement activation. Individual humans differ 1000-fold in MBL concentration, and individuals with low circulating MBL appear to be more vulnerable to infections in a number of clinical settings, especially when combined with secondary immune deficiency. The best evidence that MBL deficiency or insufficiency is physiologically relevant comes from a rapidly expanding literature of clinical studies. MBL insufficiency appears to be a significant risk factor for infections in infants, and for individuals of any age undergoing chemotherapy or post-transplant immunosuppression. Moreover, MBL appears to have a significant influence on the course of certain chronic diseases like rheumatoid arthritis and cystic fibrosis. Replacement therapy with a plasma-derived product is safe and seems promising, while recombinant MBL provides hope for large-scale therapeutic applications. Randomized clinical trials of MBL therapy, which are now on the horizon, should provide unambiguous evidence for the physiological significance of MBL in innate immunity.

Mannan-binding lectin concentration during normal human pregnancy.

Relative deficiency of mannan-binding lectin (MBL) is associated with recurrent miscarriage. To investigate whether MBL concentration alters as a result of pregnancy, serial measurements were made in 14 patients before and during normal early pregnancy. Additionally, a longitudinal study was made of one individual over several years and including two normal pregnancies. Three (20%) subjects experienced a significant increase in MBL concentration during pregnancy. It was concluded that a modest but significant increase in MBL concentration can result from pregnancy, but it is a rare occurrence in the first trimester.