Abstract. Interleukin-I (IL-1) is synthesized by and released from macrophages in response to a variety of stimuli and appears to play an essential role in virtually all inflammatory conditions. In tissues of mesenchymal origin (e.g., cartilage, muscle, bone, and soft connective tissue) ILl induces changes characteristic of both destructive as well as reparative phenomena. Previous studies with natural IL-1 of varying degrees of purity have suggested that it is capable of modulating a number of biological activities of fibroblasts. We have compared the effects of purified human recombinant (hr) IL-la and !~ on several fibroblast functions. The parameters studied include cell proliferation, chemotaxis, and production of collagen, collagenase, tissue inhibitor of metalloproteinase (TIMP), and prostaglandin (PG) E2. We observed that hrlL-ls stimulate the synthesis and accumulation of type I procollagen chains. Intracellular degradation of collagen is not altered by the hrlL-ls. Both IL-ls were observed to increase the steady-state levels of pro al(I) and pro a2(I) mRNAs, indicating that they exert control of type I procollagen gene expression at the pretranslational level. We found that both hrlL-la and 13 stimulate synthesis of TIMP, collagenase, PGE2, and growth of fibroblasts in vitro but are not chemotactic for fibroblasts. Although hrlL-la and 13 both are able to stimulate production of PGE2 by fibroblasts, inhibition of prostaglandin synthesis by indomethacin has no measurable effect on the ability of the IL-ls to stimulate cell growth or production of collagen and collagenase. Each of the IL-ls stimulated proliferation and collagen production by fibroblasts to a similar degree, however hrlL-113 was found to be less potent than hrlL-1 a in stimulating PGE2 production. These observations support the notion that IL-l~t and 13 may both modulate the degradation of collagen at sites of tissue injury by virtue of their ability to stimulate collagenase and PGE2 production by fibroblasts. Furthermore, IL-la and 13 might also direct reparative functions of fibroblasts by stimulating their proliferation and synthesis of collagen and TIMP.

When rats were injected intradermally with an oil emulsion of native type I1 collagen, they developed an inflammatory polyarthritis. The incidence and severity of arthritis increased as the amount of collagen injected was increased. Rats 4% weeks old were the most susceptible to the development of arthritis, whereas weanling and older animals were relatively resistant. There was no difference in incidence between males and females. Mononuclear cells from peripheral blood, lymph nodes, and spleen were cultured with type I1 collagen and responded maximally to a collagen concentration of 25 pg/ml. The earliest detectable response was in peripheral blood mononuclear cell cultures obtained 6 to 8 days after immunization. The response of lymph node and spleen cells tended to lag behind that of peripheral blood cells at the earlier time intervals. Antibodies were detected in sera by hemagglutination at 8 days postimmunization. Quantitation of IgM and IgG antibodies by radioimmunoassay showed good correlation with hemagglutination titers and increased binding of collagen by both classes of antibody in arthritic as compared to nonarthritic animals. It is clear that the de- velopment of both humoral and cellular immunity to type I1 collagen is associated with the development of arthritis and may be important in the pathogenesis of this disease.We have previously reported that approximately 40% of rats injected intradermally with an oil emulsion of heterologous or homologous type I1 collagen develop an inflammatory polyarthritis after a latent period of 12 to 20 days. Other types of collagen, cartilage proteoglycans, and denatured type I1 collagen are ineffective in inducing arthritis when injected in an identical manner (1,2). If animals are studied at a time when disease is well developed (21-28 days), arthritic animals have a significantly greater immune response to type I1 collagen than similarly injected nonarthritic rats (3). However, the early sequence of events in development of the immune response and its relation to clinical disease have not been adequately investigated.The present studies were undertaken to d e h e additional factors that might influence the development of collagen-induced arthritis and to evaluate the immunologic response occurring in peripheral blood, lymph nodes, and spleen at regular intervals after injection of type I1 collagen. These studies demonstrate the important influence of the immunizing dose of collagen, route of injection, and the age of the rats on the incidence and severity of arthritis. The early appearance of antibody to type I1 collagen and the quantitation of both IgG and IgM responses reported here suggest that the role of antibody to type I1 collagen in the pathogenesis of arthritis may be more significant than heretofore recognized.

The amino acid sequence of chick skin collagen alpha1-CB6A, a peptide containing 107 residues obtained from the helical region near the carboxy-terminus of the alpha1(I) chain by cyanogen bromide cleavage, has been determined. This was accomplished by automated Edman degradation of the hydroxylamine-produced fragments and of the tryptic peptides prepared with and without prior maleylation. The data show that this portion of the alpha1(I) chain from chick skin is identical in 90 percent of the residues to the corresponding peptide region of calf skin collagen reported previously.

Ear cartilage from a typical case of relapsing polychondritis was examined with the electron microscope. A large number of dense granules and vesicles, which were compatible with matrix vesicles or lysosomes, surrounded the affected chondrocytes. In less severely damaged chondrocytes, these granules and vesicles appeared to be formed by pinching off of the cytoplasmic processes or by budding from the processes. Calcification of the granules was minimal. In severely damaged chondrocytes, an admixture of these granules and cytoplasmic organelles occurred. It is speculated that many of these dense granules are lysosomal in nature and that they may produce inflammation and reduce the proteoglycan content of cartilage.

Peritoneal fluid from the abdominal cavities of guinea pigs having delayed hypersensitivity to horseradish peroxidase (HRPO) was obtained by a lavage technique before and after i.p. challenge with antigen. Macrophage migration inhibitory factor (MIF) and macrophage chemotactic factor activities were measured in peritoneal fluids from each animal. Chemotactic activity for macrophages was maximal 24 hr after i.p. challenge and was absent thereafter. MIF activity was maximal in peritoneal fluid 24 to 48 hr after challenge. Macrophages were present in greatest numbers in peritoneal fluid 24 hr after challenge and returned almost to control levels at 48 hr. Macrophages in 48-hr fluid were larger and exhibited more intense cytoplasmic staining for nonspecific esterases when compared to those in 0-hr fluid. The m.w. of MIF obtained from culture supernatants of HRPO-stimulated guinea pig lymphocytes and 48-hr peritoneal fluid were found to be virtually identical, 58,000 and 54,000 daltons, respectively. MIF from these in vitro and in vivo sources were similarly resistant to heating at 56°C for 30 min but were both destroyed by incubation with insoluble trypsin.