(2005) observed a suppression of antibody-specific T cell responses mediated by mosquito saliva and dependent on mast cells and IL-10 expression.A 2006 study suggests mosquito saliva can also decrease expression of interferon−α/β during early mosquito-borne virus infection. The contribution of type I interferons (IFN) in recovery from infection with viruses has been demonstrated in vivo by the therapeutic and prophylactic effects of administration of IFN inducers or IFN itself, and different research suggests mosquito saliva exacerbates West Nile virus infection, as well as other mosquito-transmitted viruses.Studies in humanized mice bearing a reconstituted human immune system have suggested potential impact of mosquito saliva in humans. Work published in 2018 from the Baylor College of Medicine using such humanized mice came to several conclusions, among them being that mosquito saliva led to an increase in natural killer T cells in peripheral blood; to an overall decrease in ex vivo cytokine production by peripheral blood mononuclear cells (PBMCs); changes to proportions of subsets of PBMCs; changes in the prevalence of T cell subtypes across organs; and changes to circulating levels of cytokines. Egg development and blood digestion
Most species of mosquito require a blood meal to begin the process of egg development. Females with poor larval nutrition may need to ingest sugar or a preliminary blood meal before their ovarian follicles can reach their resting stage. Once the follicles have reached the resting stage, digestion of a sufficiently large blood meal triggers a hormonal cascade that leads to egg development.
Alpha-glucosidase activity is elevated in the posterior midgut after feeding in response to the blood meal, whereas activity in the anterior midgut is consistent with a nectar-processing role for this midgut region. Ecology
Distribution
Mosquitoes are cosmopolitan (world-wide): they are in every land region except Antarctica and a few islands with polar or subpolar climates. Iceland is such an island, being essentially free of mosquitoes.The absence of mosquitoes in Iceland and similar regions is probably because of quirks of their climate, which differs in some respects from mainland regions. At the start of the uninterrupted continental winter of Greenland and the northern regions of Eurasia and America, the pupa enters diapause under the ice that covers sufficiently deep water. The imago emerges only after the ice breaks in late spring. In Iceland, the weather is less predictable. In mid-winter it frequently warms up suddenly, causing the ice to break, but then to freeze again after a few days. By that time the mosquitoes will have emerged from their pupae, but the new freeze sets in before they can complete their life cycle. Any anautogenous adult mosquito would need a host to supply a blood meal before it could lay viable eggs; it would need time to mate, mature the eggs and oviposit in suitable wetlands.