The production of migration inhibition factor (MIF) by human peripheral blood lymphocytes and guinea pig lymph node lymphocytes, in response to mitogen, concanavalin A, or antigen, tuberculin, has been studied. Suppressor cells have been depleted by in vitro ageing of cultures for 24 hours, and this has resulted in a significant increase in MIF activity. Reconstitution of the aged lymphocyte population by the addition of fresh lymphocytes results in a suppression of MIF production. When lymphocytes, which have been cultured for 24 hours in the presence of antigen or mitogen to generate suppressor cells, are added to aged cultures MIF production is inhibited. These results suggest that suppressor cells play a regulatory role in the production of MIF.

Animals↗

PubMed1975

Structures of three new steroidal sapogenins from Dioscorea prazeri.

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Hydroxysteroids↗

PubMedDate not supplied

Structural perturbation of alpha-crystallin and its chaperone-like activity.

alpha-Crystallin is a multimeric lenticular protein that has recently been shown to be expressed in several non-lenticular tissues as well. It is shown to prevent aggregation of non-native proteins as a molecular chaperone. By using a non-thermal aggregation model, we could show that this process is temperature-dependent. We investigated the chaperone-like activity of alpha-crystallin towards photo-induced aggregation of gamma-crystallin, aggregation of insulin and on the refolding induced aggregation of beta- and gamma-crystallins. We observed that alpha-crystallin could prevent photo-aggregation of gamma-crystallin and this chaperone-like activity of alpha-crystallin is enhanced several fold at temperatures above 30 degrees C. This enhancement parallels the exposure of its hydrophobic surfaces as a function of temperature, probed using hydrophobic fluorescent probes such as pyrene and 8-anilinonaphthalene-1-sulfonate. We, therefore, concluded that alpha-crystallin prevents the aggregation of other proteins by providing appropriately placed hydrophobic surfaces; a structural transition above 30 degrees C involving enhanced or re-organized hydrophobic surfaces of alpha-crystallin is important for its chaperone-like activity. We also addressed the issue of conformational aspects of target proteins and found that their aggregation prone molten globule states bind to alpha-crystallin. We trace these developments and discuss some new lines that suggest the role of tertiary structural aspects in the chaperone process.

Animals↗