Biomedical subjects
Publications and source records attributed to J Panijel.
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It has been shown previously that cells from long-term calf lymphoid cell cultures (8--9 months) contain factors able to inhibit in vitro immune response. We report here that extracts prepared from lymph node cells freshly removed from old cows also contain similar factors inhibiting primary and secondary in vitro responses of mouse spleen cells against sheep red blood cells. These extracts do not affect cell viability nor stimulation with B or T mitogen (LPS or Con A). They do not affect production of antibodies by previously differentiated cells such as plasmocytomes or hybridomes. The active factor(s) appear(s) to behave as protein(s) of molecular weight about 10 000. Our results suggest that analogous "ageing" events occur either in long-term cultures of lymphocytes or in lymphoid cells of senescent animals. These phenomena would involve production or activation of specific factor(s) capable of inhibiting antibody synthesis by intervening at the level of differentiation of lymphocytes stimulated either by T-dependent or T-independent antigens.
When guinea-pig lymph node cells were exposed to ConA in a culture medium lacking glutamine or cysteine, no DNA synthesis occurred. The addition of the missing acid to ConA-treated lymphocytes submitted to glutamine or cysteine starvation for 40 h allowed the synthesis of DNA to take place after a period of only 10-12 h. The synthesis of DNA is preceded by a rapid increase of 3H-uridine incorporation into RNA and of 3H-leucine incorporation into protein which occurred a few hours after addition of the missing amino acid. When cycloheximide was added to lymphocytes exposed to ConA in a glutamine or cysteine deprived medium, a relative enhancement of uridine incorporation was observed. No such effect was provoked by puromycin. These results suggest the possibility of a control system in lymphocytes similar to those described in microbial cells for amino acid control of RNA synthesis.
Using a microculture system which permits the survival of very small numbers of active lymphoid cells, the frequency of units of response towards two non-crossing antigens, SRBC and phage phi17, is determined in long term cultures of calf lymph node cells. A much higher frequency, as hitherto reported using mouse spleen cells, is found: about one active unit of response towards either antigen per 8 x 10(3) cells. When microcultures are stimulated with the two antigens, phenomena of antigenic competition occur: a 40% depression of the response to each antigen takes place when the antigens are added simultaneously or when the second antigen is added at a later time within the first 2 days. When the interval between the two stimulations is 3 days, only the response to the first antigen takes place at the same level of frequency as that obtained from cultures which are stimulated only with this antigen. These results support the hypothesis of pluripotentiality of lymphoid cells. Each immunocompetent cell would contain a large repertoire of specificities; triggering with antigen would provoke a two stage differentiation process. The first stage lasting until 48 hours after stimulation would be reversible, whereas the second stage would be irreversible. The latter step would involve the phenomena of specific antibody synthesis. Theoretical implications of these results are discussed.