Innate Immunity

Professor Krystyna Kotełko was working as a microbiologist at the University of Łódź (Poland). Her main object of study was the LPS (endotoxin) of opportunistic urinary pathogens from the genus Proteus. She demonstrated, for the first time, the presence of uronic acids and amino acids, as well as two heptoses (L-glycero-D-manno-heptose and D-glycero-D-manno-heptose) and hexosamines in Proteus LPS, and developed a classification scheme of the Proteus LPS into chemotypes. Prof Kotełko also initiated studies on the chemical structure of Proteus O-specific polysaccharide and investigations on the serological specificity of this part of LPS, as well its core region. She also analysed the virulence factors of these bacteria, such as haemolysin and invasiveness.

Macrophages are important innate immune cells that respond to microbial insults. In response to multi-bacterial infection, the macrophage activation state may change upon exposure to nascent mediators, which results in different bacterial killing mechanism(s). In this study, we utilized two respiratory bacterial pathogens, Mycobacterium bovis (Bacillus Calmette Guẻrin, BCG) and Francisella tularensis live vaccine strain (LVS) with different phagocyte evasion mechanisms, as model microbes to assess the influence of initial bacterial infection on the macrophage response to secondary infection. Non-activated (M0) macrophages or activated M2-polarized cells (J774 cells transfected with the mouse IL-4 gene) were first infected with BCG for 24–48 h, subsequently challenged with LVS, and the results of inhibition of LVS replication in the macrophages was assessed. BCG infection in M0 macrophages activated TLR2-MyD88 and Mincle-CARD9 signaling pathways, stimulating nitric oxide (NO) production and enhanced killing of LVS. BCG infection had little effect on LVS escape from phagosomes into the cytosol in M0 macrophages. In contrast, M2-polarized macrophages exhibited enhanced endosomal acidification, as well as inhibiting LVS replication. Pre-infection with BCG did not induce NO production and thus did not further reduce LVS replication. This study provides a model for studies of the complexity of macrophage activation in response to multi-bacterial infection.

The aim of this study is to describe the prevalence of single single-nucleotide polymorphisms (SNPs) as well as their combinations in genes encoding proteins involved in the immune response in children with bacterial meningitis. The prospective study group consisted of 39 children with bacterial meningitis and 49 family members surveyed between 2012 and 2016. Eleven SNPs in seven genes involved in immune response were analysed. The mean number of minor frequency alleles (MAF) of studied SNPs was lowest in the control group and highest in patients with pneumococcal meningitis. We found that carrying ≥6 MAF of studied SNPs was associated with an increased risk of pneumococcal meningitis. The prevalence of risky variants was noted to be higher in patients with pneumococcal meningitis as compared to the control group. In conclusion, genetic factors are a relevant factor in determining the susceptibility to bacterial meningitis. A statistically significant cumulative effect of mutated variants on increasing the risk of bacterial meningitis was detected. Combining all three SNPs in MBL2 improves the prediction of susceptibility to pneumococcal meningitis. Analysis of risky alleles can help indicate people prone to the disease who are ‘gene-immunocompromised’.

Childhood asthma represents a worldwide problem, involving genetic, immune defense and environmental components. MicroRNAs (miRs) are non-coding, single-stranded RNAs involved in immune regulation. The aim was to evaluate clinical potential of plasma miR-21 and miR-146a involved in T helper differentiation in childhood asthma and non-asthmatic controls. Group 1 consisted of 27 asthmatic children receiving inhaled corticosteroids (ICSs), which was compared to group 2 with 21 healthy control children. All patients were assessed by pulmonary function tests. miR-21 and miR-146a expression levels were determined by real-time quantitative PCR, and IL-13 was measured using ELISA. Group 1 showed significant up-regulation of plasma miR-21 and miR-146a levels with mean values 42.6-fold and 4.7-fold higher than average expression, respectively, in group 2. miR-21 levels positively correlated with IL-13 levels and eosinophil percentage, while miR-146a only correlated to eosinophil percentage. There was a linear association between each of miR-21 and miR-146a expression and FEV1 (forced expiratory volume in the first second), miR-21 and miR-146a are up-regulated in asthmatic children. miR-21 served as a better asthma biomarker. Association between both markers and FEV1 points to their role in determining asthma outcome following ICS treatment. miR-21 and miR-146a play a role in eosinophilic endotypic classification of asthma.

Innate immunity natural Abs (NAbs) execute a number of functions, including protection and surveillance. Despite active research, the stimuli that induce the formation of NAbs are still described only hypothetically. Here, we compared repertoires of anti-glycan Abs in the peripheral blood of mice that received per os various bacteria. The repertoires of Abs of mice primed in this way were compared using a microarray that included about 350 glycans, as well as 150 bacterial polysaccharides. Sterile mice did not possess anti-glycan Abs. Oral inoculation of a single strain or combination of two to four strains of bacteria, as well as putting the animals on short-term nutrition with non-sterile food, did not contribute significantly to the formation of Abs, whereas a single gavage of digested food of non-sterile mice induced the formation of a repertoire close to the natural ones. Interestingly, the priming with polysaccharide Ags (in a composition of the bacterial cell envelope), that is, dominant Ags of bacteria, led to the induction of Abs against typical glycans of mammalian glycoproteins and glycolipids (e.g. Abs of the ABH blood group system) that do not have a structural similarity to the polysaccharides. The results support the importance of early contact with a naïve immune system with microorganisms of the environment to form a normal NAbs repertoire.