Host immunity

The suitability of a host depends on whether the parasitoid can evade or suppress the host s internal defense or immune mechanism(s). It has been suggested (Doutt, 1963 Salt, 1963) that by the careful placement of their progeny on the host (ectoparasitoids), within certain tissues (i.e., fat body, ganglion), or in certain stages (eggs) many species of parasitoids evade the host s defense. However, this assumption needs critical investigation. 

In some cases a non-cellular capsule is formed, believed to consist of melanin (Vey and Gotz, 1975). Melanin may also be involved in cellular encapsulation (Nappi, 1975 Salt, 1963). In both cases it is believed that these capsules kill the parasitoid egg or larvae by blocking the oxygen supply and source of nutrition (Fisher, 1971 Salt, 1970a). In some parasitoid Diptera the encapsulation response is often manipulated to the parasitoid s benefit (Salt, 1968) by forming around the parasitoid a sheath, attached at one end to a trachea supplying O2 and at the other end to the hemolymph through which the parasitoid feeds. 

A third means of parasitoid elimination, discovered by Arthur and Ewen (1975), is referred to as cuticular encystment. After parasitism, the host forms a small cyst of the posterior dorsal cuticle which consists of a separation of the cuticle from the epidermis with a space containing hemolymph. The parasitoid egg or larva migrates into the cyst which is shed at the next molt. 

There is little doubt that chemicals play an important role in the internal defense and counterdefenses that have evolved during the evolution of the various parasitoid-host relationships. Currently too little is known about the chemicals involved in internal recognition and defense to develop any overall concepts. 

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The active immunotherapeutic approach is specific and based on the premise that tumor antigens are immunogenic and the host is sufficientiy immunocompetent to mount an effective immune response to an autologous tumor. Theoretically, a weak or suppressed host immune system that had allowed the formation of a tumor may be overridden by active immunization or immunostimulation. In practice, vaccines composed of so-called autologous tumor extracts have been used to treat patients with malignant melanoma (73), and purified melanoma tumor-associated antigens have been used to ehcit antibody responses in melanoma patients (74). 

Immunological reactions of the host to either the delivery vehicle or its cargo are another concern. The host immune response might not only eliminate the vector... 

Manno CS, Pierce GF, Arrada VR et al (2006) Successful transduction of liver in hemophilia by AAV-Factor IX and limitations imposed by the host immune response. Nat Med 12(3) 342-347... 

Hematopoietic (blood) cells transport oxygen and carbon dioxide, contribute to host immunity, and facilitate blood clotting [1], A complex, interrelated, and multistep process, called hematopoiesis, controls the production as well as the development of specific marrow cells from immature precursor cells to functional mature blood cells. This well-regulated process also allows for replacement of cells lost through daily physiologic activities. The proliferation of precursor cells, the maturation of these into mature cells, and the survival of hematopoietic cells require the presence of specific growth factors. 

A number of chimerized, humanized, and one human mAb have now been approved for therapeutic use in humans in the treatment of autoimmunity, malignancy, infection and cardiovascular disease (Table 1). Some of the currently licensed mAb will be discussed here. A much larger number of mAb are currently being evaluated in Phase I, II and III trials. In general, chimeric, humanized and human mAb are very well tolerated with few side effects. Chimeric or humanized mAb still have the potential to evoke host immune response to the variable domains or CDRs of the antibody so-called HACA (human anti-chimeric antibody) or HAHA (human anti-human antibody) responses, although these responses are uncommon. Short-lived and occasionally severe infusion-related acute hypersensitivity reactions such as fever, skin itching, shivering, respiratory compromise and low blood pressure sometimes occur-. Such effects may... 

Gene Therapeutic Strategies that Act via Host Immune Effector Mechanisms.283... 

Hoschele D (2006) Cell culture models for the investigation of NRTI-induced mitochondrial toxicity. Relevance for the prediction of clinical toxicity. Toxicol In Vitro 20(5) 535-546 Itescu S, Brancato LJ et al (1989) A sicca syndrome in HIV infection association with HLA-DR5 and CDS lymphocytosis. Lancet 2(8661) 466 68 Itescu S, Brancato LJ et al (1990) A diffuse infiltrative CDS lymphocytosis syndrome in human immunodeficiency virus (HIV) infection a host immune response associated with HLA-DR5. Ann Intern Med 112(1) 3-10... 

Antibodies against HCV (anti-HCV) in the blood indicate infection with the HCV. If the infection persists for more than 6 months and viral replication is confirmed by HCV RNA levels, then the person has chronic hepatitis C. Chronic disease may be due to an ineffective host immune system against the HCV. Cytotoxic T lymphocytes are ineffective in eradicating the HCV, thus allowing persistent damage to hepatic cells. Therefore, immunocompromised individuals are less likely to eliminate HCV.12... 

Multiple factors play a role in the development of AOM. Viral infection of the nasopharynx impairs eustachian tube function and causes mucosal inflammation, impairing mucociliary clearance and promoting bacterial proliferation and infection. Children are predisposed to AOM because their eustachian tubes are shorter, more flaccid, and more horizontal than adults, which make them less functional for drainage and protection of the middle ear from bacterial entry. Clinical signs and symptoms of AOM are the result of host immune response and damage to cells caused by inflammatory mediators such as tumor necrosis factor and interleukins that are released from bacteria.4... 

Genital herpes, caused by herpes simplex virus (HSV) types 1 and 2, is a common STI for which there is no cure. Once latency is established, neither competent host immunity nor therapeutic agents can eradicate the virus. Currently, there is... 

Treatment is based on several factors including likelihood of patient compliance, whether it is the first or a recurrent episode, host immunity, and pregnancy. However, patient response has been linked to the time it takes to initiate treatment after symptom onset. 

Commensal or environmental fungi that are typically harmless can become invasive mycoses when the host immune defenses are impaired. Host immune suppression and risk for opportunistic mycoses can be broadly classified into three categories (1) quantitative or qualitative deficits in neutrophil function, (2) deficits in cell-mediated immunity, and (3) disruption of mechanical/and or microbiologic barriers. 

The effectors of the mammalian host immune attack against filaria include reactive oxygen intermediates. Filarial nematodes express glutathione peroxidase, thioredoxin peroxidase and superoxide dismutase at their surface - enzymes believed to protect the nematode from this attack (Selkirk et al., 1998). A bacterial catalase gene has been identified that most probably derives from the endosymbiont genome (Henkle-Duhrsen et al., 1998) this enzyme may contribute with other enzymes to the protection of both Wolbachia and its nematode host from oxygen radicals. 

Interaction of Host Immunity and Temperature on Developmental Route... 

For much of its life cycle a parasite s environment is its host. A principal, and potentially lethal, feature of this environment is the host immune response. Diversity in parasites interactions with this aspect of their environment may therefore be expected. The host immune response varies between different hosts and so, if this is considered as a selection pressure, it may produce the ideal conditions for the generation of diversity in immune-mediated parasite-host interactions. 

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