Tumor antigenic targets

Tumor cells in the first metastasis escaped immune recognition due to selective loss of HLA haplotype, but maintain the expression of HLA-A2 antigen. In contrast, in the second metastasis immune escape from immune dominant antigen-specific T cell responses were mediated by HLA class I downregulation which results in the impaired presentation of this epitope, whereas another tumor antigen-specific epitope was presented. This resulted in the shift of the dominant T cell response to a subdominant targeted response. 

In addition to monoclonal antibody or chemotherapy, immunotherapy has been developed to target tumor antigen for the treatment of FL. The unique sequence of the protein, so-called idiotype (Id) protein, can be a target of immunotherapy. Because Id protein can induce humoral and cellular immune responses against idiotype protein, vaccination with Id protein can decrease the risk of progression. However, the mechanism of anti-Id response has been unclear. 

Immunoliposomes targeted to other tumor antigens were also studied by several research groups. " The immunoliposomes generally showed more significant therapeutic responses than non-targeted liposomes or the free drug. 

Monoclonal antibodies can vary tremendously in terms of isotype, construction (animal derived, chimeric, humanized, bound to toxin), ability to activate complement, binding avidity, target specificity, and whether it binds and blocks or binds and activates the receptor. Monoclonal antibodies may be directed toward soluble or membrane bound receptors or receptor ligands, tumor antigens, growth factor or their receptors. Therefore toxicity and side effects are equally variable [68]. 

Monoclonal antibody therapy is based on the ability to target markers and bind to cell membrane antigens with great specificity. Many times the enhanced specificity demonstrated toward the tumor antigens allows normal cells to be protected against harmful effects, unlike conventional chemotherapy. There are several mechanisms by which monoclonal antibodies destroy or prevent further replication of malignant cells. Some monoclonal antibodies utilize tumor immunology and components of the host natural defense mechanism to exert their desired effect. For example, monoclonal antibodies can utilize tumor effector cells to promote tumor cell lysis or have the ability to directly modulate tumor function. 

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