Polymorphisms of the tumor necrosis factor alpha locus among autoimmune disease susceptible and resistant inbred rat strains

Macrophages and HLA-Class II Alleles in Multiple Sclerosis: Insights in Therapeutic Dynamics

Antigen presentation is a crucial mechanism that drives the T cell-mediated immune response and the development of Multiple Sclerosis (MS). Genetic alterations within the highly variable Major Histocompatibility Complex Class II (MHC II) have been proven to result in significant changes in the molecular basis of antigen presentation and the clinical course of patients with both Adult-Onset MS (AOMS) and Pediatric-Onset MS (POMS). Among the numerous polymorphisms of the Human Leucocyte Antigens (HLA), within MHC II complex, HLA-DRB1*15:01 has been labeled, in Caucasian ethnic groups, as a high-risk allele for MS due to the ability of its structure to increase affinity to Myelin Basic Protein (MBP) epitopes. This characteristic, among others, in the context of the trimolecular complex or immunological synapsis, provides the foundation for autoimmunity triggered by environmental or endogenous factors. As with all professional antigen presenting cells, macrophages are characterized by the expression of MHC II and are often implicated in the formation of MS lesions. Increased presence of M1 macrophages in MS patients has been associated both with progression and onset of the disease, each involving separate but similar mechanisms. In this critical narrative review, we focus on macrophages, discussing how HLA genetic alterations can promote dysregulation of this population's homeostasis in the periphery and the Central Nervous System (CNS). We also explore the potential interconnection in observed pathological macrophage mechanisms and the function of the diverse structure of HLA alleles in neurodegenerative CNS, seen in MS, by comparing available clinical with molecular data through the prism of HLA-immunogenetics. Finally, we discuss available and experimental pharmacological approaches for MS targeting the trimolecular complex that are based on cell phenotype modulation and HLA genotype involvement and try to reveal fertile ground for the potential development of novel drugs.

No association between tumor necrosis factor-alpha production and gene polymorphisms among inbred rat strains

Differences in spontaneous allograft acceptance after liver transplantation among inbred rat strains might be explained by variation in the local production of TNF-alpha as a potent mediator of the inflammatory response. In this study, we hypothesize that nucleotide differences in the rat Tnf gene influence TNF-alpha protein expression. As such, polymorphisms in the Tnf gene may also provide a possible explanation for differences in survival of allogeneic liver grafts among inbred rat strains. We therefore investigated the capacity of mononuclear cells to produce TNF-alpha in response to a mitogenic stimulus and the Tnf locus was sequenced in six different inbred rat strains. Among the six strains (AUG, BN, DA, LEW, PVG and WF), 44 nucleotide differences including 36 single nucleotide polymorphisms (SNPs), five simple sequence length polymorphisms, two deletions and one insertion, were found in the Tnf gene. Although, the inbred rat strains differed significantly in mean levels of maximum TNF-alpha production (P = 0.001), no associations were found with nucleotide differences within the Tnf gene. In conclusion, our results indicate that differential in vitro TNF-alpha responses among inbred rat strains are not associated with nucleotide differences within non-coding regulatory regions of the rat TNF-alpha gene. Without an established relationship between polymorphisms and expression of the TNF-alpha gene, it is preliminary to address a possible association of Tnf gene polymorphisms with rat liver allograft survival.

Inhibition of tumour necrosis factor-alpha by antisense targeting produces immunophenotypical and morphological changes in injury-activated microglia and macrophages

Microglia respond in a stereotypical pattern to a diverse array of pathological states. These changes are coupled to morphological and immunophenotypical alterations and the release of a variety of reactive species, trophic factors and cytokines that modify both microglia and their cellular environment. We examined whether a microglial-produced cytokine, tumour necrosis factor-alpha (TNF-alpha), was involved in the maintenance of microglial activation after spinal cord injury by selective inhibition using TNF-alpha antisense deoxyoligonucleotides (ASOs). Microglia and macrophages harvested from 3 d post-contused rat spinal cord were large and rounded (86.3 +/- 9.6%). They were GSA-IB4-positive (GSA-IB4(+)) (Griffonia simplicifolia lectin, microglia specific; 94.8 +/- 5.1%), strongly OX-42 positive (raised against a type 3 complement/integrin receptor, CD11b; 78.9 +/- 9.1%), ED-1 positive (a lysosomal marker shown to correlate well with immune cell activation; 97.2 +/- 2.6%) and IIA positive (antibody recognizes major histocompatibility complex II; 57.2 +/- 5.6%), indicative of fully activated cells, for up to 48 h after plating. These cells also secreted significant amounts of TNF-alpha (up to 436 pg/microg total protein, 16 h). Fluoroscein isothiocyanate-labelled TNF-alpha ASOs (5, 50 and 200 nm) added to the culture medium were taken up very efficiently into the cells (> 90% cells) and significantly reduced TNF-alpha production by up to 92% (26.5 pg/microg total protein, 16 h, 200 nm TNF-alpha ASOs). Furthermore, few of the treated cells at this time were round (5.4 +/- 2.7%), having become predominantly spindle shaped (74.9 +/- 6.3%) or stellate (21.4 +/- 2.7%); immunophenotypically, although all of them remained GSA-IB4 positive (91.6 +/- 6.2%), many were weakly OX-42 positive and few expressed either ED-1 (12.9 +/- 2.5%) or IIA (19.8 +/- 7.4%). Thus, the secretion of TNF-alpha early in spinal cord injury may be involved in autoactivating microglia/macrophages. However, at the peak of microglial activation after injury, the activation state of microglia/macrophages is not stable and this process may still be reversible by blocking TNF-alpha.