Hürthle Cells Predict Hypothyroidism in Interferon-γ Transgenic Mice of Different Genetic Backgrounds

Hürthle cells have long been described in Hashimoto thyroiditis but remain of undetermined significance. We have previously shown that Hürthle cells and hypothyroidism develop in C57BL/6J mice expressing interferon-γ (IFNγ) in the thyroid. To assess the influence of genetic backgrounds on Hürthle cell development, we crossed C57BL/6J IFNγ transgenic mice to 14 strains and analyzed thyroid histopathology and function in a cohort of 389 mice (225 transgenic and 164 wild type) using a multiple linear regression model that also included strain, sex, genotype, and major histocompatibility complex haplotype. We then queried the Johns Hopkins surgical pathology electronic archive for “Hashimoto” and/or “thyroiditis” keywords, reviewed the reports, and reexamined the Hashimoto slides. Hürthle cells were markedly affected by the genetic background: they were prominent and associated with hypothyroidism in the C57BL/6J, C57BL/6ByJ, C57BL/10J, C57BLKS/J, C57L/J, C58/J, and BPN/3J IFNγ transgenic strains, whereas they are mild or absent in the BPH/2J, BPL/1J, LP/J, CBA/J, Balb/cJ, DBA/1J, and NOD/ShiLtJ strains. Hürthle cells were the strongest predictor of hypothyroidism after adjusting for all the other covariates in the regression model. Interestingly, transgenic mice of the BPL/1J, DBA/1J, and NOD/ShiLtJ strains developed a marked accumulation of intrathyroidal brown adipocytes that was significantly associated with improved thyroid function. Hürthle cells were mentioned in 23% of the Hashimoto reports but increased to 79% upon our slide review. This study reports a novel association of Hürhtle cells and brown adipocytes on thyroid function that should prompt a reconsideration of their significance and role in pathogenesis of autoimmune thyroiditis.

Extensive Polymorphism and Evidence of Immune Selection in a Highly Dominant Antigen Recognized by Bovine CD8 T Cells Specific for Theileria annulata

ABSTRACTAlthough parasite strain-restricted CD8 T cell responses have been described for several protozoa, the precise role of antigenic variability in immunity is poorly understood. The tick-borne protozoan parasiteTheileria annulatainfects leukocytes and causes an acute, often fatal lymphoproliferative disease in cattle. Building on previous evidence of strain-restricted CD8 T cell responses toT. annulata, this study set out to identify and characterize the variability of the target antigens. Three antigens were identified by screening expressed parasite cDNAs with specific CD8 T cell lines. In cattle expressing the A10 class I major histocompatibility complex haplotype, A10-restricted CD8 T cell responses were shown to be focused entirely on a single dominant epitope in one of these antigens (Ta9). Sequencing of the Ta9 gene from field isolates ofT. annulatademonstrated extensive sequence divergence, resulting in amino acid polymorphism within the A10-restricted epitope and a second A14-restricted epitope. Statistical analysis of the allelic sequences revealed evidence of positive selection for amino acid substitutions within the region encoding the CD8 T cell epitopes. Sequence differences in the A10-restricted epitope were shown to result in differential recognition by individual CD8 T cell clones, while clones also differed in their ability to recognize different alleles. Moreover, the representation of these clonal specificities within the responding CD8 T cell populations differed between animals. As well as providing an explanation for incomplete protection observed after heterologous parasite challenge of vaccinated cattle, these results have important implications for the choice of antigens for the development of novel subunit vaccines.

The requirement for NKG2D in NK cell–mediated rejection of parental bone marrow grafts is determined by MHC class I expressed by the graft recipient

Natural killer (NK) cells provide a unique barrier to semiallogeneic bone marrow (BM) transplantation. In the setting where the parents donate to the F1 offspring, rejection of parental bone marrow occurs. This “hybrid resistance” is completely NK cell dependent, as T cells in the F1 recipient tolerate parental grafts. Previously, we demonstrated that rejection of BALB/c parental BM by (BALB/c × C57BL/6) F1-recipient NK cells is dependent on the NKG2D-activating receptor, whereas rejection of parental C57BL/6 BM does not require NKG2D. BALB/c and B6 mice possess different NKG2D ligand genes and express these ligands differently on reconstituting BM cells. Herein, we show that the requirement for NKG2D in rejection depends on the major histocompatibility complex haplotype of donor cells and not the differences in the expression of NKG2D ligands. NKG2D stimulation of NK cell–mediated rejection was required to overcome inhibition induced by H-2Dd when it engaged an inhibitory Ly49 receptor, whereas rejection of parental BM expressing the ligand, H-2Kb, did not require NKG2D. Thus, interactions between the inhibitory receptors on F1 NK cells and parental major histocompatibility complex class I ligands determine whether activation via NKG2D is required to achieve the threshold for rejection of parental BM grafts.

Lagochilascaris minor: Susceptibility and Resistance to Experimental Infection in Mice Is Independent of H-2aHaplotype and Correlates with the Immune Response in Immunized Animals

Recently, we demonstrated that C57BL/6 mice are more susceptible to experimental lagochilascariosis than BALB/c mice. To investigate the pattern of infection and the role of the genetic background on susceptibility to infection, we studied experimental lagochilascariosis in H-2aidentical B10.A and A/J mice. Infected B10.A mice had a lower survival ratio and more severe lesions in the lungs than did A/J mice. Splenocytes of A/J mice immunized with the crude extract of the parasite showed increased proliferation and produced a higher level of interleukin 10 and interferon-γin the presence of CE or concanavalin A when compared to B10.A mice. This suggests that resistance of A/J mice may be due to less severe lesions in lungs and other organs and a better immune response to parasite antigens. This paper provides evidence that major histocompatibility complex haplotype does not influence the survival to experimental infection withL. minor.

Major Histocompatibility Complex Haplotype Determines hsp70-Dependent Protection against Measles Virus Neurovirulence

ABSTRACT In vitro studies show that hsp70 promotes gene expression for multiple viral families, although there are few reports on the in vivo significance of virus-hsp70 interaction. Previously we showed that hsp70-dependent stimulation of Edmonston measles virus (Ed MeV) transcription caused an increased cytopathic effect and mortality in transgenic hsp70-overexpressing C57BL/6 mice (H-2 b ). The response to MeV infection is influenced by the major histocompatibility complex haplotype; H-2 d mice are resistant to brain infection due to robust antiviral immune responses, whereas H-2 b mice are susceptible due to deficiencies in this response. We therefore tested the hypothesis that the outcome of MeV-hsp70 interaction may be dependent upon the host H-2 haplotype. The impact of selective neuronal hsp70 overexpression on Ed MeV brain infection was tested with congenic C57BL/10 H-2 d neonatal mice. In this context, hsp70 overexpression conferred complete protection against virus-induced mortality, compared to >30% mortality in nontransgenic mice. Selective depletion of T-cell populations showed that transgenic mice exhibit a diminished reliance on T cells for protection. Brain transcript analysis indicated enhanced innate immune activation and signaling through Toll-like receptors 2 and 4 at early times postinfection for transgenic infected mice relative to those for nontransgenic infected mice. Collectively, results suggest that hsp70 can enhance innate antiviral immunity through Toll-like receptor signaling, supporting a protective role for physiological responses that enhance tissue levels of hsp70 (e.g., fever), and that the H-2 haplotype determines the effectiveness of this response.

Transmission of Simian Immunodeficiency Virus Carrying Multiple Cytotoxic T-Lymphocyte Escape Mutations with Diminished Replicative Ability Can Result in AIDS Progression in Rhesus Macaques

ABSTRACT Cytotoxic T-lymphocyte (CTL) responses frequently select for immunodeficiency virus mutations that result in escape from CTL recognition with viral fitness costs. The replication in vivo of such viruses carrying not single but multiple escape mutations in the absence of the CTL pressure has remained undetermined. Here, we have examined the replication of simian immunodeficiency virus (SIV) with five gag mutations selected in a macaque possessing the major histocompatibility complex haplotype 90-120-Ia after its transmission into 90-120-Ia-negative macaques. Our results showed that even such a “crippled” SIV infection can result in persistent viral replication, multiple reversions, and AIDS progression.

N-Glycan Processing Deficiency Promotes Spontaneous Inflammatory Demyelination and Neurodegeneration

Multiple sclerosis (MS) is characterized by inflammatory demyelination of axons and neurodegeneration, the latter inadequately modeled in experimental autoimmune encephalomyelitis (EAE). Susceptibility of inbred mouse strains to EAE is in part determined by major histocompatibility complex haplotype; however, other molecular mechanisms remain elusive. Galectins bind GlcNAc-branched N-glycans attached to surface glycoproteins, forming a molecular lattice that restricts lateral movement and endocytosis of glycoproteins. GlcNAc branching negatively regulates T cell activity and autoimmunity, and when absent in neurons, induces apoptosis in vivo in young adult mice. We find that EAE susceptible mouse strains PL/J, SJL, and NOD have reduced GlcNAc branching. PL/J mice display the lowest levels, partial deficiencies in N-acetylglucosaminyltransferase I, II, and V (i.e. Mgat1, -2, and -5), T cell hyperactivity and spontaneous late onset inflammatory demyelination and neurodegeneration; phenotypes markedly enhanced by Mgat5+/- and Mgat5-/- backgrounds in a gene dose-dependent manner. Spontaneous disease is transferable and characterized by progressive paralysis, tremor, dystonia, neuronophagia, and axonal damage in both demyelinated lesions and normal white matter, phenocopying progressive MS. Our data identify hypomorphic Golgi processing as an inherited trait that determines susceptibility to EAE, provides a unique spontaneous model of MS, and suggests GlcNAc-branching deficiency may promote T cell-mediated demyelination and neurodegeneration in MS.

Maintenance of Antibody to Pathogen Epitopes Generated by Segmental Gene Conversion Is Highly Dynamic during Long-Term Persistent Infection

ABSTRACT Multiple bacterial and protozoal pathogens utilize gene conversion to generate rapid intrahost antigenic variation. Both large- and small-genome pathogens expand the size of the variant pool via a combinatorial process in which oligonucleotide segments from distinct donor loci are recombined in various combinations into expression sites. Although the potential combinatorial diversity generated by this segmental gene conversion mechanism is quite large, the functional variant pool depends on whether immune responses against the recombined segments are generated and maintained, regardless of their specific combinatorial context. This question was addressed by tracking the Anaplasma marginale variant population and corresponding segment-specific immunoglobulin G (IgG) antibody responses during long-term infection. Antibody was induced early in A. marginale infection, predominately against the surface-exposed hypervariable region (HVR) rather than against the invariant conserved flanking domains, and these HVR oligopeptides were most immunogenic at the time of acute bacteremia, when the variant population is derived via recombination from a single donor locus. However antibody to HVR oligopeptides was not consistently maintained during persistent infection, despite reexpression of the same segment, although in a different combinatorial context. This dynamic antibody recognition over time was not attributable to the major histocompatibility complex haplotype of individual animals or use of specific msp2 donor alleles. In contrast, the position and context of an individual oligopeptide segment within the HVR were significant determinants of antibody recognition. The results unify the genetic potential of segmental gene conversion with escape from antibody recognition and identify immunological effects of variant mosaic structure.