1、Evasion of Immunity IVertebrate and invertebrate immune systems.Dr. Jo HamiltonParasitology BSIntroduction. Successful parasites have evolved strategies for survival & development in both invertebrate and vertebrate hosts. The goal of a parasite is to propagate within the host and be transmitted to
2、the next host. The goal of the parasitised host is to cure or limit the infection. During the next three lectures we will investigate strategies used by parasites to evade the host immune response. In this session we will revisit the immune system of both vertebrates and invertebrates.Objectives and
3、 learning outcomes. By the end of this session students should be: Familiar with fundamental biology of vertebrate & invertebrate immune systems. Familiar with the concept of innate and acquired immunity in vertebrates. Recognise that there is only innate immunity in invertebrates. Recognise the key
4、 players in both vertebrate and invertebrate immune systems.Immunity. Resistance to infection is called immunity. The term “immunity” is derived from the Greek word “immunis” meaning exempt. There are two types of immunity in vertebrates.Innate immunity present from birth.Acquired immunity result of
5、 infection or vaccination. Invertebrates only posses innate immunity.Innate immunity in vertebrates (also known as non-specific or natural immunity).Characteristics: Present from birth. Non-specific - acts on many organisms and does not show specificity. Does not become more efficient on subsequent
6、exposure to same organisms. Innate immunity in vertebrates.Non-specific Host Defences include: Mechanical / physical barriers skin, mucosal surfaces. Prevention of stasis peristalsis, flow of urine, upward movement of secretions in bronchial tree, coughing, vomiting. Innate immunity in vertebrates.
7、Chemical defences - Low pH of stomach contents, secretion of fatty acids in the skin. Biological defence complement, lysozyme, interferons, antimicrobial peptides, kinins, adhesion molecules, hormones, lactoferrin. Cellular defence - e.g. phagocytes.Innate immunity in vertebrates.Some of the key pla
8、yers in innate immunity to consider in more detail are: Complement. Opsonization. Phagocytosis & the oxidative burst. Inflammation.Innate immunity in vertebrates complement. Complement. - complex of 17 proteins present in normal serum. 2 pathways classical & alternative. Innate immunity in vertebrat
9、es classical complement pathway. Antigen-antibody complex forms, constant region of antibody changes shape. Activates C1, acquires esterase activity. Activated C1 activates C2 & C4 which activates C3, etc. Eventually, C8 & C9 activated forming membrane attack complex (MAC) - pores in target cell membrane - lysis.
