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The effects of in vivo modulation of murine collagen induced arthritis with monoclonal anti-CD4 antibodies, monoclonal anti-Ia antibodies, and gamma interferon are reviewed. We detail the mechanism of action of monoclonal anti-CD4 antibody on humoral and cell mediated immune responses and discuss the implications for designing therapeutic strategies. To further explore the induction of collagen induced arthritis, a syngeneic cell transfer system using collagen primed T lymphocytes is described. This cell transfer system provides an opportunity to study the role of CD4 positive T lymphocytes in arthritis induction during a short, defined time period.

We have prepared a monoclonal antibody specific for a major 94,000 dalton protein from the brush border membrane of rabbit kidney cortex. The monoclonal antibody was used for the immunoaffinity purification of this protein after solubilization of brush border membranes with octylglucoside. The 94,000 dalton protein is a peptidase capable of cleaving the Gly3-Phe4 bond of methionine-enkephalin. Identification of this peptidase as a previously described 94,000 dalton enkephalinase of kidney cortex was confirmed by its sensitivity to EDTA and inhibitors such as thiorphan and phosphoramidon.

Proopiomelanocortin, the common glycoprotein precursor to adrenocorticotropin (ACTH) and beta-lipotropin (beta-LPH), is the most abundant protein synthesized in rat neurointermediate lobes. It represents 30% of the total amount of radioactive proteins obtained after a 1-h pulse incubation with [3H]phenylalanine. Several forms of this protein can be separated by a high-resolution two-dimensional gel electrophoresis technique. The three most abundant species which can be reproducibly characterized by their apparent molecular weights (Mr) and isoelectric points (pI) were called form I (Mr 34 000; pI 8.2), form II (Mr 36 000; pI 8.2), and form III (Mr 35 000; pI 7.3). Additional minor forms, representing together approximately 30% of the total forms I, II, and III combined, are also observed. They have very close molecular weights but differ by their isoelectric points. When glycosylation is prevented by tunicamycin, forms I and II are replaced by a new molecule with the same pI of 8.2 but a slightly lower Mr (32 000). This form is referred to as form T1. Similarly, form III is replaced by form T2 (Mr 33 000; pI 7.3). Forms T1 and T2 are supposed to be nonglycoslyated peptides. They were further characterized by microsequencing and peptide mapping. They both have the same N-terminal amino acid sequence with leucine residues in positions 3 and 11, and they both contain identical [3H]phenylalanine-labeled tryptic fragments, two of them corresponding to the sequences 1-8 of ACTH and 61-69 of beta-LPH. However, a limited digestion with the Staphylococcus aureus (V8 strain) protease generates a collection of peptides different for each form. These results suggest the presence of at least two different gene products corresponding to the major forms of proopiomelanocortin in the rat pars intermedia.

Proopiomelanocortin (POMC), the common precursor to beta-endorphin and alpha-melanocyte-stimulating hormone synthesized in rat intermediate lobe cells, exhibits both charge and size heterogeneity on two-dimensional gels. Pulse-labeling and pulse-chase studies revealed that this heterogeneity is due to co- and post-translational modifications of a single common polypeptide. Short 5-min-pulse incubation with [3H]phenylalanine allowed the preferential labeling of two major forms characterized by an identical isoelectric point (8.2), but slightly different apparent molecular weights (MW = 34,000 and 36,000). These peptides could be labeled with [3H]mannose and the analysis of their tryptic fragments by high-pressure liquid chromatography revealed that they correspond to polypeptides bearing one or two N-linked carbohydrate side chains. Accumulation of more acidic forms was observed during subsequent chase incubations in the absence of phenylalanine. These acidic forms were shown to incorporate sulfate and (or) phosphate groups. Sulfation and phosphorylation occurred on POMC within 5 min after its synthesis and were concomitant with the processing of the N-linked carbohydrates from the high mannose to the complex structure. Finally, partial digestion of the phosphorylated and nonphosphorylated analogs of POMC with either Staphylococcus aureus (V8 strain) protease or chymotrypsin suggests that the presence of a phosphate group may alter POMC sensitivity to exogenously added proteases.