Mosquito Immunity to the Malaria Parasite

This chapter provides a detailed outline of the cellular and molecular components and mechanisms that are involved in the mosquito's defense against malaria parasites. The mosquito's defense against pathogens involves not only structural barriers, such as the exoskeleton and the peritrophic matrix that is secreted to line the midgut after feeding, but also a variety of cellular and humoral mechanisms, which will be discussed in subsequent sections. Transmission of the Plasmodium parasite requires the successful completion of a complex life cycle in the Anopheles mosquito. This complex life cycle is a challenge to the parasite, since it must encounter such a variety of environments within the mosquito before being transmitted to the next human host. Pattern recognition receptors (PRRs) are responsible for detecting the Plasmodium parasite in mosquitoes, identifying it as foreign, and then triggering the signaling pathways that ultimately lead to killing or containing the pathogen. Signaling amplification cascades generally lead to the encapsulation of Plasmodium, while immune signaling pathways allow transcription factors to translocate to the nucleus, where they initiate the transcription of immune genes. The Anopheles mosquito has become an important model organism for the understanding of how invertebrate immunity functions but, more importantly, its immune system directly interferes with a disease affecting millions of people worldwide, making it relevant to public health.