The future of acute phase proteins (APPs) in science is discussed in this paper. Many functions and associated pathological processes of APPs are unknown. Extrahepatic formation in local tissues needs attention. Local serum amyloid A (SAA) formation may be involved in deposition of AA-amyloid induced by conformational change of SAA resulting in amyloid formation, having tremendous food safety implications. Amyloidogenesis is enhanced in mouse fed beta pleated sheet-rich proteins. The local amyloid in joints of chicken and mammary corpora amylacea is discussed. Differences in glycosylation of glycoproteins among the APPs, as has been shown for alpha1-acid glycoprotein, have to be considered. More knowledge on the reactivity patterns may lead to implication of APPs in the diagnostics and staging of a disease. Calculation of an index from values of several acute phase variables increases the power of APPs in monitoring unhealthy individuals in animal populations. Vaccinations, just as infections in eliciting acute phase response seem to limit the profitability of vaccines because acute phase reactions are contra-productive in view of muscle anabolism. Interest is focused on amino acid patterns and vitamins in view of dietary nutrition effect on sick and convalescing animals. When inexpensive methodology such as liquid phase methods (nephelometry, turbidimetry) or protein array technology for rapid APP measurement is available, APPs have a future in routine diagnostics. Specific groups of patients may be screened or populations monitored by using APP.
In domestic brown layer fowl, reactive amyloidosis of internal organs, such as liver and spleen, and of the joints is a common disorder. In a variety of amyloid types including the AA-amyloid of the chicken, in addition to amyloid fibrils, proteoglycans and glycosaminoglycans (GAGs) are found on immunohistochemistry or after extraction. The aim of the present report is to study amyloid fibrils for the ultrastructural location of GAGs by cuprolinic blue staining and immunogold labeling. Rabbit antichicken AA antiserum was used for the immunogold labeling on conventionally embedded and cryoembedded liver tissue and revealed similar results. Therefore conventional blocks could be used for further analysis. Cuprolinic blue staining was performed on blocks of joint tissue in which clearly discernable rod-shaped glycoproteins were encountered in between collagen fibrils. Moreover, it appeared to stain larger deposits which might represent amyloid. Postlabeling with the immunogold method of the cuprolinic blue-stained tissue proved that cuprolinic blue positive fibrils represented AA-amyloid fibrils. Therefore, it was concluded that the GAGs which appeared to colocalize with the fibrillar microanatomy of amyloid, represent a structural part of the amyloid fibrils and that the avian amyloid fibrils may be considered as a pathological proteoglycan.
To investigate whether superantigen (SAG) from endogenous mouse mammary tumor virus functions as an immunogenic or a tumorigenic factor in tumor development, the BALB/c myeloma cell line FO was transfected with the SAG gene from the 3 Mtv-50 long terminal repeat (LTR) open reading frame (ORF), the product of which was specific for V6. All five transfectants expressing Mtv-50 LTR ORF mRNA showed stimulatory activity for V6 T-cell hybridomas in vitro; this activity was inhibited by the addition of anti-Mtv-7 monoclonal antibody (MAb) or anti-major histocompatibility complex class II I-A d and I-E d MAb. All transfectants with the SAG gene grew more rapidly than did mock transfectants in BALB/c mice after subcutaneous inoculation, whereas all clones, including mock transfectants, grew equally well in athymic nude mice. A significant fraction of V6 T cells selectively expressed activation markers, including CD44 high , CD62L low , and CD69 high , and produced large amounts of interleukin 5 (IL-5) and IL-6 in BALB/c mice inoculated with transfectants. These results suggested that the expression of viral SAG enhances the tumorigenicity of a myeloma cell line through the stimulation of SAG-reactive T cells.Mouse mammary tumor virus (MMTV) is a replicationcompetent B-type murine retrovirus and causes mammary adenocarcinomas in some strains of laboratory mice (30). MMTV can be transmitted exogenously through milk and endogenously through a germ line as proviruses (Mtv). Both exogenous MMTV and endogenous Mtv proviruses have an open reading frame (ORF) encoding superantigen (SAG) in the 3Ј long terminal repeat (LTR); SAG binds to major histocompatibility complex (MHC) class II molecules and leads to stimulation and consequent deletion of mature T cells bearing particular V gene products (1,2,10,21,22,(27)(28)(29)34). As T-cell recognition of SAG is mediated predominantly by the T-cell receptor (TCR) V domain, SAG can stimulate much higher proportions of T cells than can conventional peptide antigens (3,19). After B cells are infected with exogenous MMTV, viral SAGs are presented on the cell surface in the context of MHC class II molecules. Through the SAG-MHC class II complex, the infected B cells then induce the proliferation of CD4 ϩ T cells bearing specific TCR V chains (11,24,44). These T cells lead to the expansion of infected B cells, resulting in amplification of the infection with MMTV (3,5,20,39,41). On the other hand, SAG expression from inherited provirus usually leads to depletion of immature T cells expressing reactive TCR  chains during intrathymic T-cell development (14). Thus, the characteristic of SAG for strong T-cell stimulation is critical in successful infection of the mammary gland for exogenous MMTV and in skewing the T-cell repertoire via clonal deletion for endogenous MMTV. Since most of the T cells recognizing SAG expressed by MMTV, irrespective of their maturation stage, are finally deleted after stimulation with SAG, a direct role of SAG in tumorigenicity for a mammary tumor seems unlike...
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