M1/M2 macrophages and their overlaps - myth or reality?

Macrophages represent heterogeneous cell population with important roles in defence mechanisms and in homoeostasis. Tissue macrophages from diverse anatomical locations adopt distinct activation states. M1 and M2 macrophages are two polarized forms of mononuclear phagocyte in vitro differentiation with distinct phenotypic patterns and functional properties, but in vivo, there is a wide range of different macrophage phenotypes in between depending on the microenvironment and natural signals they receive. In human infections, pathogens use different strategies to combat macrophages and these strategies include shaping the macrophage polarization towards one or another phenotype. Macrophages infiltrating the tumours can affect the patient's prognosis. M2 macrophages have been shown to promote tumour growth, while M1 macrophages provide both tumour-promoting and anti-tumour properties. In autoimmune diseases, both prolonged M1 activation, as well as altered M2 function can contribute to their onset and activity. In human atherosclerotic lesions, macrophages expressing both M1 and M2 profiles have been detected as one of the potential factors affecting occurrence of cardiovascular diseases. In allergic inflammation, T2 cytokines drive macrophage polarization towards M2 profiles, which promote airway inflammation and remodelling. M1 macrophages in transplantations seem to contribute to acute rejection, while M2 macrophages promote the fibrosis of the graft. The view of pro-inflammatory M1 macrophages and M2 macrophages suppressing inflammation seems to be an oversimplification because these cells exploit very high level of plasticity and represent a large scale of different immunophenotypes with overlapping properties. In this respect, it would be more precise to describe macrophages as M1-like and M2-like.

Chemokine Profiles Are Affected in Serum of Patients with Acute Rejection of Kidney Allograft.

Kidney allograft transplantation improved the prognosis and quality of life of patients with end-stage renal diseases but the occurrence of acute rejection represents a limitation of the final outcome. Noninvasive biomarkers are needed as well as further advancements in the understanding of immune mechanisms of reaction to the allograft. Our study of 138 patients focused on one-year monitoring of serum concentrations of 12 chemokines regulating the recruitment of different immune cells into transplanted allograft and on in vitro regulation of the same chemokines release by interactions of renal proximal epithelial cells with monocyte/macrophage cell line stimulated with TNF alpha. In a group of 44 patients with acute rejection, higher serum pretransplant levels of CXCL1, CXCL5, CXCL6, CCL2, CCL21, and particularly CXCL10 and CX3CL1(both p < 0.001) were found suggesting their higher proinflammatory status as compared to subjects with the uncomplicated outcome. In samples collected at the day of biopsy positive for acute rejection, chemokines CXCL9 and CXCL11 attracting preferentially Th1 lymphocytes were found to be upregulated. In our in vitro model with TNF alpha induction, renal proximal epithelial cells seemed to be a more potent source of chemokines attracting neutrophils as compared to monocyte/macrophage cell line but the coculture of these cells potentiated release of neutrophilic chemokines CXCL5 and CXCL6. Similar augmentation of chemokine production was found also in the case of CCL2. On the other hand, adding of monocytes/macrophages to a culture of renal epithelial cells suppressed the release of CXCL10 and CXCL11 attracting T lymphocytes. We assume from our data that in kidney allograft transplantation, chemokines attracting neutrophils, T lymphocytes, and monocytes are induced simultaneously and measurement some of them in combination might be used as biomarkers of acute rejection. Mutual cell-cell interactions of immune cells with renal parenchyma seem to be important for fine regulation of chemokine release.

Dynamic changes of B-cell compartments in kidney transplantation: lack of transitional B cells is associated with allograft rejection.

B cells play an important role in the immune responses which affect the outcomes of kidney allografts. Dynamic changes of B-cell compartments in clinical kidney transplantation are still poorly understood. B-cell subsets were prospectively monitored using flow cytometry for 1 year in 98 kidney transplant recipients. Data were correlated with immunosuppression and clinical outcomes. An increase in the total population of B lymphocytes was observed during the first week after transplantation. The level of IgM(high) CD38(high) CD24(high) transitional B cells reduced significantly up until the third month, with partial repopulation in the first year. Lower numbers of transitional B cells in the third month were associated with higher risk of graft rejection. IgM(+) IgD(+) CD27(-) naive B cells did not change within follow-up. IgM(+) CD27(+) nonswitched memory B cells and IgM(-) CD27(+) switched memory B cells increased on post-operative day 7. IgM(-) CD38(high) CD27(high) plasmablasts showed similar kinetics during the first post-transplant year, similar to transitional B cells. In conclusion, sensitized kidney transplant recipients as well as those with either acute or chronic rejection within the first post-transplant year exhibited lower levels of transitional B cells. Therefore, these data further support the hypothesis that transitional B cells have a protective role in kidney transplantation.

Attenuated neutralization, maintained specificity: Humoral response to SARS-CoV-2 booster in kidney allograft recipients.

Despite the lower virulence of current SARS-CoV-2 variants and high rates of vaccinated and previously infected subjects, COVID-19 remains a persistent threat in kidney transplant recipients (KTRs). This study evaluated the parameters of anti-SARS-CoV-2 antibody production in 120 KTRs. The production of neutralizing antibodies in KTRs, following booster vaccination with the mRNA vaccine BNT162b2, was significantly decreased and their decline was faster than in healthy subjects. Factors predisposing to the downregulation of anti-SARS-CoV-2 neutralizing antibodies included age, lower estimated glomerular filtration rate, and a full dose of mycophenolate mofetil. Neutralizing antibodies correlated with those targeting the SARS-CoV-2 receptor binding domain (RBD), SARS-CoV-2 Spike trimmer, total SARS-CoV-2 S1 protein, as well as with antibodies to the deadly SARS-CoV-1 virus. No cross-reactivity was found with antibodies against seasonal coronaviruses. KTRs exhibited lower postvaccination production of neutralizing antibodies against SARS-CoV-2; however, the specificity of their humoral response did not differ compared to healthy subjects.

Manumycin A downregulates release of proinflammatory cytokines from TNF alpha stimulated human monocytes.

Macrolide antibiotics such as azithromycin or clarithromycin are known to have potent anti-inflammatory and immunomodulatory effects but these properties cannot be widely used due to a risk of bacterial resistance. We studied another polyketide antibiotic, structurally related manumycin A known as a streptomycete derived farnesyltransferase inhibitor with limited antibacterial effects, with respect to its potential regulation of mRNA expression of several genes associated with proinflammatory responses. Downregulation of mRNA for IL-6, TLR-8, IL-1 beta and IL-10 was found in THP-1 cells after 4h stimulation with TNF alpha in the presence of manumycin A and downregulated TLR-8 and EGR-1 genes were observed after 8h. Among the genes upregulated in response to manumycin were HMOX-1, TNFRSF10A, IL-1R1, TICAM2, NLRP12 after 4h and only IL-1R1 after 8h. Furthermore, manumycin A was found to inhibit IL-1beta, IL-6, and IL-8 production in TNF alpha stimulated THP-1 cells and peripheral blood monocytes in a dose dependent manner (0.25-1 µM of manumycin A) without affecting cell viability. Cell viability of blood monocytes decreased by about 30% at manumycin A doses of 2-5 µM. Manumycin A also inhibited IL-18 release from THP-1 cells, while in cultures of blood monocytes, this cytokine was not detectable. That manumycin A mediated downregulation of proinflammatory genes in human monocytes confirmed by a measurement of cytokine levels in culture supernatants, together with a very limited effect on cell viability, might suggest potential anti-inflammatory properties of this polyketide antibiotic.

High Prevalence of Neutrophil Cytoplasmic Autoantibodies in Infants with Food Protein-Induced Proctitis/Proctocolitis: Autoimmunity Involvement?

Background. Food protein-induced proctitis/proctocolitis (FPIP) is the most common noninfectious colitis in children in the first year of life. Along with the overall clinical symptoms, diarrhoea and rectal bleeding are the main manifestations of the disease. There is no routine noninvasive test that would be specific for this type of colitis. The aim of our study was to find a noninvasive laboratory test or tests that may be helpful in differential diagnosis of food protein-induced proctitis/proctocolitis. Methods. ANA, ANCA, ASCA, a-EMA, a-tTg, specific IgE, total IgE, IgG, IgA, IgM, and concentration of serum calprotectin were measured in a group of 25 patients with colitis and 18 children with other diagnoses. Results. Atypical-pANCA antibodies of IgG isotype were detected in the sera of 24 patients by the method of indirect immunofluorescence, and 5 patients showed also the positivity of IgA isotype. In control samples these autoantibodies were not detected. Other autoantibodies were not demonstrated in either patient or control group. Conclusions. Of the parameters tested in noninfectious colitis, atypical-pANCA on ethanol-fixed granulocytes appears to be a suitable serological marker of food protein-induced proctitis/proctocolitis and suggests a possible involvement of an autoimmune mechanisms in the pathogenesis of this disease.