In order to maintain immunological tolerance to self and non-self antigens, one’s T regulatory (Treg) cells play a critical role in the regulation of detrimental inflammation. Treg cells inhibit the immune system in a variety of ways, some of which are contact-dependent and the others are soluble factors. Extracellular vesicles (EVs) are mainly secretory membrane structures that play a pivotal role in intercellular communication in both the local and systemic environments, enabling the transport of proteins, lipids, and nucleic acids between immune and non-immune cells. A number of studies have shown that Treg-derived EVs are specially formulated intercellular exchanging devices capable of regulating immunological responses by producing a cell-free tolerogenic milieu. Some of the processes suggested include miRNA-induced gene shutdown and upmodulation, surface protein activity, and enzyme transfer. Instead of being influenced by external circumstances like Tregs, exosomes’ cohesive structure allows them to transmit their charge intact across the blood–brain barrier and deliver it to the target cell with particular receptors. These properties have resulted in the use of Treg-derived EVs' immunomodulatory effects moving beyond laboratory research and into preclinical applications in animal models of a variety of inflammatory, autoimmune, and transplant rejection disorders. However, insufficient evidence has been produced to permit enrollment in human clinical studies. As such, we begin our research by introducing the most potent immunosuppressive elements discovered in Treg-derived EVs elucidating likely mechanisms of action in inhibiting immunological responses. Following that, we address recent research on the potential of suppressive EVs to regulate autoimmune inflammatory responses and improve tissue transplant survival.

The calamity of the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV2), COVID-19, is still a global human tragedy. To date, no specific antiviral drug or therapy has been able to break the widespread of SARS-CoV2. It has been generally believed that stimulating protective immunity via universal vaccination is the individual strategy to manage this pandemic. Achieving an effective COVID-19 vaccine requires attention to the immunological and non-immunological standpoints that mentioned in this article. Here, we try to introduce the considerable immunological aspects, potential antigen targets, appropriate adjuvants as well as key points in the various stages of COVID-19 vaccine development. Also, the principal features of the preclinical and clinical studies of pioneering COVID-19 vaccine candidates were pointed out by reviewing the available information. Finally, we discuss the key challenges in the successful design of the COVID-19 vaccine, and address the most fundamental strengths and weaknesses of common vaccine platforms.

BACKGROUND: Since it was assumed that exercise might be a risk factor for upper respiratory tract infection (URTI), the frequency, severity and duration of URTI were assessed in female elite runners compared with matched sedentary group. METHODS: A group of elite runners (N.=20) and one of sedentary subjects (N.=20) were selected and matched one by one for their age, nutritional state, their place of living and somewhat genetic factors. These groups were observed for any signs and symptoms of upper respiratory illnesses, during 2.5 cold months of the year. RESULTS: Although the mean number of the illnesses in elite athletes (1.0 +/- 0.8) was slightly lower than the control people (1.4 +/- 0.8); there was not any statistically significant difference between them (P>0.05). Furthermore. the mean days of disease (5.4 +/- 3.8 in elite athletes vs. 5.6 +/- 3.0 in control group) showed no significant statistical difference (P>0.05). Even though elite athletes showed no severe cases of the disease, no significant difference was observed between the two groups (P>0.05). CONCLUSIONS: Elite athletes are not at greater risk for URTI and this may be due to the suitable physiological status of athletes or attributed to "repeated bout effect" phenomenon.