Serum amyloid A-derived peptides, present in human rheumatic synovial fluids, induce the secretion of interferon-gamma by human CD(4)(+) T-lymphocytes.

Serum amyloid A (SAA) is a major acute-phase protein whose biochemical functions remain largely obscure. Human rheumatic synovial fluids were screened by high performance liquid chromatography mass spectrometry for SAA-derived peptides, specifically the sequence AGLPEKY (SAA(98-104)) which was previously shown to modulate various leukocyte functions. Two such fluids were found to contain a truncated version of SAA(98-104). Synthetic SAA(98-104) and several of its analogs were shown capable of binding isolated human CD(4)(+) T-lymphocytes and stimulating them to produce interferon-gamma. Given the high acute-phase serum level of SAA and its massive proteolysis by inflammatory related enzymes, SAA-derived peptides may be involved in host defense mechanisms.

Binding of human serum amyloid P component (hSAP) to human neutrophils.

Human serum amyloid P component (hSAP) and human C-reactive protein (hCRP) are normal serum constituents related to the pentraxin family of plasma proteins. hSAP has morphological and immunochemical identity and extensive sequence similarity to the amyloid P (AP) component found in normal tissues and particularly in amyloid deposits. hCRP and its proteolytic products have been previously shown to bind and to interact with various types of human leukocytes. Binding-displacement experiments with 125I-labeled hSAP and hCRP show that both proteins have specific high-affinity binding sites on normal human polymorphonuclear leukocytes (PMN) and each can compete efficiently with the binding of the other. Scatchard analysis of hSAP-displacement curves reveals a heterogeneous population of hSAP-binding sites existing on the PMN cells, among them about 300,000 low-affinity binding sites with Kd < or = 5 x 10(-6) M and about 30,000 high-affinity binding sites with Kd < or = 5 x 10(-8) M. hAP was found to be degraded by enzymes from human neutrophils to yield a mixture of low-molecular-mass peptides, similarly to the case of CRP reported previously. The binding of hSAP can be efficiently inhibited by this peptide mixture. The results suggest that both hCRP and hSAP, together with related peptides, may participate in vivo in an unknown mechanism of regulation of human neutrophils.

Inhibition of cell adhesion to glycoproteins of the extracellular matrix by peptides corresponding to serum amyloid A. Toward understanding the physiological role of an enigmatic protein.

Synthetic peptides related to amino acid residues 29-42 of human serum amyloid A (SAA), Tyr-Ile-Gly-Ser-Asp-Lys-Tyr-Phe-His-Ala-Arg-Gly-Asn-Tyr, were found to inhibit the adhesion of human T-lymphocytes and of mouse M4 melanoma cells to surfaces coated with the major cell adhesive glycoproteins of the extracellular matrix, laminin or fibronectin. Correspondingly inhibitory activity was manifested by the entire 14-residue peptide, by its YIGSD laminin-related domain, and by RGN, the fibronectin-related domain. Intact recombinant SAA (rSAA) and its 1-76 fragment, an amyloid A (AA) protein, also inhibited cell adhesion. The peptides did not inhibit collagen and ADP-induced aggregation of human platelets. Proteolysis of SAA by lysosomal enzymes originating from human neutrophils led to generation of specific peptide segments some of which pertain to the 29-42 domain. It is suggested that the acute-phase protein SAA might be involved, either directly or via its peptide fragments, in inhibition of inflammatory reactions or metastatic processes which depend on integrin and possibly other extracellular-matrix-specific receptors mediated specific recognition and interactions with immobilized components of blood-vessel walls.

Dermatomyositis in a patient with malignant melanoma.

The association between dermatomyositis and malignancy has been a controversial issue discussed in the literature. We will describe a rare case of a 34-year-old woman with a 6-year history of malignant melanoma and new onset dermatomyositis. To the best of our knowledge only 8 such cases have been previously reported in the literature.

Polyglandular autoimmune syndrome, type 2.

We have described two patients with Addison's disease and associated endocrinopathies, a condition termed polyglandular autoimmune (PGA) syndrome, type 2. One of our patients also had autoimmune hypothyroid disease, and the other had premature gonadal failure and Hashimoto's thyroiditis. This syndrome shows that glandular disorders tend to occur together. It has been suggested that an HLA-associated genetic predisposition coupled with environmental factors triggers an autoimmune process resulting in glandular hypofunction or hyperfunction. We stress the necessity for evaluation of every individual with idiopathic Addison's disease for associated endocrinopathies.