Controlling CD4+ immune cells infiltration of the brain is a leading aim in designing therapeutic strategies for a range of neuropathological disorders such as; multiple sclerosis, Alzheimer and depression. CD4+ T cells are a highly heterogeneous and reprogrammable family, that includes various distinctive cell types such as Th17, Th1, and Tregs. Interestingly Th17 and Tregs share a related transcriptomic profile, where the TGFβ-SMADS pathway plays a fundamental role in regulating the differentiation of both of these cell types. However, Th17 could be highly pathogenic and was shown to promote inflammation in various neuropathological disorders. Conversely, Treg is anti-inflammatory and is known to inhibit Th17. It could be noticed that Th17 frequencies of infiltration of the blood-brain barrier (BBB) in various neurological disorders are significantly upregulated. However, Treg infiltration numbers are significantly low. The reasons behind these contradicting observations are still unknown. In this perspective, we propose that the difference in the TCR repertoire diversity, diapedesis pathways, chemokine expression and mechanical properties of these two cell types could be contributing to answering this intriguing question.

Depression is a complex neuropsychiatric disorder characterized by pervasive feelings of sadness, hopelessness, and cognitive impairments that can profoundly impact an individual's quality of life. Despite extensive research efforts, the precise mechanisms underlying depression remain elusive. Recent studies have highlighted the intricate interplay between the immune system and the central nervous system in the pathophysiology of depression. In this context, CD4+ T cells, a key component of the adaptive immune system, have emerged as potential players in the neuroinflammatory processes associated with depression. Concurrently, Brain-Derived Neurotrophic Factor (BDNF), a multifunctional neurotrophin, has garnered significant attention for its roles in neural plasticity, mood regulation, and cognitive function. This review paper explores the intriguing intersection between CD4+ T cells and BDNF in the context of depression and delves into the exciting prospects it offers for therapeutic interventions. By examining the intricate crosstalk between the immune system and the neurotrophic factors, we aim to shed light on the potential avenues for novel therapeutic strategies in the treatment of depression.

Cancer metastasis into the brain constitutes one of the most severe but not uncommon development of cancer growth. Several factors control how cancer types interact with the brain to establish metastasis These factors include system of migration, system of infiltration of the blood-brain barrier and the interaction with host cells (e.g., neurons, astrocytes) and the immune system fight against metastasis in the brain. Although, brain radiotherapy is the main treatment procedure carried out to treat, new therapies are emerging that constitute a glimpse of hope for increasing the diminutive life expectancy currently forecasted to cancer patients who are facing the prospectus of brain metastasis. However applying these therapeutic strategies has been has not been effective. Thus there is a need for better understanding of the metastasis process in order to suggest novel therapeutic targets. In this review, we follow the journey of various cancer cells from their primary location through the various process that they undergo including EMT, penetration of the ECM, intravasation, extravasation and infiltration of the blood brain barrier ending up with colonization and angiogenesis. In each phase, we focus on molecules that could potentially be drug target candidates.

Sepsis is a serious disease that can lead to mortality. The etiology of the disease is connected to how the body as a host reacts toward microbes such as bacteria, viruses, and fungi invasion. Current research shows that during sepsis, the reaction toward microbe attacks takes two main phases. The first is known as a cytokine storm, while the second is a vicious cycle of pro-inflammatory responses followed by a strict anti-inflammatory response led by CD4+ Tregs. Various immunomodulatory therapies have been proposed to break the cycle of pro- and anti-inflammatory reactions to sepsis. However, clinical trials did not show promising results, indicating further research into the mechanism that Treg uses to inhibit proinflammatory reactions. We used next-generation sequencing (NGS) analysis of bulk RNA-seq and single-cell RNA-seq data to examine the exact molecular pathways used by Treg to inhibit the immune response in sepsis. Our approach identified ACOD1 (Aconitate Decarboxylase 1) as a primary mediator of Treg suppression of immune cells. We identified and validated CD36 as a downstream target of ACOD1. CD36 is a known metabolite regulator in Tregs. Taken together, our results indicate that targeting ACOD1 could prove valuable in regulating Treg function during sepsis.