Autoimmunity: beyond the immune system

Effects of biological sex and pregnancy in experimental autoimmune encephalomyelitis: It's complicated

Experimental autoimmune encephalomyelitis (EAE) can be induced in many animal strains by inoculation with central nervous system antigens and adjuvant or by the passive transfer of lymphocytes reactive with these antigens and is widely used as an animal model for multiple sclerosis (MS). There are reports that female sex and pregnancy affect EAE. Here we review the effects of biological sex and the effects of pregnancy on the clinical features (including disease susceptibility) and pathophysiology of EAE. We also review reports of the possible mechanisms underlying these differences. These include sex-related differences in the immune system and in the central nervous system, the effects of hormones and the sex chromosomes and molecules unique to pregnancy. We also review sex differences in the response to factors that can modify the course of EAE. Our conclusion is that the effects of biological sex in EAE vary amongst animal models and should not be widely extrapolated. In EAE, it is therefore essential that studies looking at the effects of biological sex or pregnancy give full information about the model that is used (i.e. animal strain, sex, the inducing antigen, timing of EAE induction in relation to pregnancy, etc.). In addition, it would be preferable if more than one EAE model were used, to show if any observed effects are generalizable. This is clearly a field that requires further work. However, understanding of the mechanisms of sex differences could lead to greater understanding of EAE, and suggest possible therapies for MS.

The role of epigenetic mechanisms and processes in autoimmune disorders

The lack of complete concordance of autoimmune disease in identical twins suggests that nongenetic factors play a major role in determining disease susceptibility. In this review, we consider how epigenetic mechanisms could affect the immune system and effector mechanisms in autoimmunity and/or the target organ of autoimmunity and thus affect the development of autoimmune diseases. We also consider the types of stimuli that lead to epigenetic modifications and how these relate to the epidemiology of autoimmune diseases and the biological pathways operative in different autoimmune diseases. Increasing our knowledge of these epigenetic mechanisms and processes will increase the prospects for controlling or preventing autoimmune diseases in the future through the use of drugs that target the epigenetic pathways.

Female reproductive issues in multiple sclerosis

Multiple sclerosis (MS) is more common in females than males and frequently affects women during their reproductive years. Thus, issues surrounding pregnancy and reproduction are of concern to women with MS. This review documents studies that shed light on reproductive issues in women with MS. The available literature was searched for papers relating to pregnancy and MS. Pregnancy is protective in MS in the short term, perhaps due to modulation of the immune system in pregnancy. It also possible that changes in the brain in pregnancy could protect against the effects of inflammation. The long-term effects of pregnancy also seem to be beneficial to MS, perhaps due to long-term epigenetic changes or possibly due to the effects of fetal microchimerism. Obstetric outcomes in women with MS are similar to those in the general population. In addition, there have been no reports of severe fetal abnormalities in babies exposed to first-line MS therapies. There is no good evidence that breast-feeding is protective in MS. There is no evidence that oral contraceptive pill use predisposes to MS, nor influences the clinical course of MS. After menopause, there is possible deterioration of MS, but it’s difficult to disentangle this from the effects of aging and the natural progressive history of MS. The strong biological effect of pregnancy on MS deserves further study, so that these mechanisms can possibly be replicated as therapies for MS.

Thymus microenvironment in human primary immunodeficiency diseases

PURPOSE OF REVIEW

Severe combined immunodeficiencies represent a heterogeneous group of genetic disorders affecting genes of both early and late steps in lymphocytes development, a process tightly controlled by thymic epithelial cells. Detailed analysis of thymic morphology aids to the assessment of the severity of the immune disorder and may be critical to the understanding of the role of the genetic defects in the pathophysiology of these diseases. In this review, we highlight recent advancements in the characterization of the thymic microenvironment in primary immunodeficiencies.

RECENT FINDINGS

Crosstalk between thymocytes and thymic epithelial cells is essential to preserve thymic architecture and function, and therefore to promote T-cell maturation and development of self-tolerance. Early severe defects in T-cell development result in profound abnormalities of thymic epithelial cells differentiation with loss of AIRE expression and severe reduction of thymic dendritic and T-regulatory cells. Differently, later defects in T-cell development that are permissive for normal thymocytes development allow cortico-medullary differentiation with partially preserved AIRE expression and dendritic/T-regulatory cells distribution. Hypomorphic mutations in the same genes partially permissive to T-cell development may result in a more complex phenotype with immunodysreactivity and peculiar thymic alterations.

SUMMARY

Although the molecular and genetic bases of primary immunodeficiencies directly aid to both diagnosis and management of the patients, the detailed analysis of thymic morphology critically contributes to unveil the pathophysiology of these diseases.