We have used crossed immunoelectrophoresis to identify and establish the relative amounts of serum proteins secreted by a differentiated cell line (Fao) derived from a Reuber H35 rat hepatoma. Our results show that these cells secrete at least 15 plasma proteins. Ten of these: albumin, alpha 1-antitrypsin, alpha 1-lipoprotein, alpha 1-macroglobulin, alpha 1-antichymotrypsin, GC-globulin (transcalciferin), fibronectin, hemopexin, transferrin and the C3 component of complement have been identified. To examine the feasibility of using the Fao cell line as a model for studies on the regulation of hepatic protein secretion, we measured the relative amounts of 10 serum proteins secreted into the growth medium after exposure of these cells to dibutyryl cyclic AMP, hydrocortisone and a combination of both compounds. We also examined the effects of growth temperature (33.5 degrees, 37 degrees and 39 degrees C) and the removal of fetal calf serum from the growth medium on the relative amounts of these proteins secreted. We found that the rates of secretion of most of the serum proteins were altered by one or more of the treatments used in these experiments. In addition, detectable levels of secretion of three serum proteins, fibronectin and two unidentified, occurred only under certain of the experimental conditions. These results demonstrate that the pattern of proteins secreted from Fao cells can be experimentally altered and indicate that this cell line may be a useful model for studies on the control of hepatic protein secretion.

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PubMedDate not supplied

Mechanisms involved in the antibody-mediated suppression of tuberculin-type delayed hypersensitivity: the effects of antigen concentration on tolerance induction, the ability of antigen-antibody complexes to render tolerant and the effects of toleration on antigen-induced in vitro proliferation.

Long-lived tuberculin-type delayed hypersensitivity to chicken conalbumin (CA), as measured by skin-reaction, is inhibited in CAF1 mice by passively administered hyperimmune mouse antiserum to CA. We describe here three new parameters of this inhibition: (1) induction of tolerance is not dependent on the concentration of antigen used to sensitize, even when 3.6-fold more antigen is administered than the tolerizing antibodies can bind; (2) antigen-antibody complexes formed in vitro can inhibit; and (3) although induction rather than reaction is suppressed by antiserum treatment, early stages of sensitization are not inhibited. This is shown by the capacity of inguinal lymph node cells from suppressed mice to proliferate in vitro, in response to antigen, 7 and 14 days after sensitization and antiserum treatment. In fact, this in vitro proliferative response is specifically enhanced in suppressed mice on day 7. These results suggest a complex mechanism of antibody-mediated immunoregulation.

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