Biological and chemical characterization of an immune antigen-RNA species derived from hepatocyte polysomes

Making sense from antisense: a review of experimental data and developing ideas on sense--antisense peptide recognition

Peptides encoded in the antisense strand of DNA have been predicted and found experimentally to bind to sense peptides and proteins with significant selectivity and affinity. Such sense--antisense peptide recognition has been observed in many systems, most often by detecting binding between immobilized and soluble interaction partners. Data obtained so far on sequence and solvent dependence of interaction support a hydrophobic-hydrophilic (amphipathic) model of peptide recognition. Nonetheless, the mechanistic understanding of this type of molecular recognition remains incomplete. Improving this understanding likely will require expanding the types of characteristics measured for sense--antisense peptide complexes and hence the types of analytical methods applied to such interactions. Understanding the mechanism of sense--antisense peptide recognition also may provide insights into mechanisms of native (sense) peptide and protein interactions and protein folding. Such insight may be helpful to learn how to design macromolecular recognition agents in technology for separation, diagnostics and therapeutics.

Antigen handling in ageing. III. Age-related changes in antigen handling by liver parenchymal and nonparenchymal cells

This is a continuation of our earlier studies on antigen handling and the ageing process which have shown the liver to be a major site of antigen retention in the body. This paper reports on the uptake and cellular distribution in relatively pure isolates of the principal cell types of the liver of [35S]sulfanilate-azo-bovine serum albumin (35S-BSA) injected into F-344 rats of ages 4, 12 and 28 months. In all three cell types [hepatocytes (H), Kupffer cells (K) and endothelial cells (E)] antigen retention peaks in the 12-month age class and then exhibits a significant decline in the 28-month age class; K and E cells retain more antigen per cell than do H cells. All three cell types metabolize antigen to nucleopeptides and this transformed antigen is immunologically active; K and E cells metabolize antigen to nucleopeptides more effectively than do H cells. A significant age-related difference is found when nucleopeptides from either H, K or E cells are used to stimulate an antigen-specific lymphoproliferative response in vitro: nucleopeptides from 4-month and 12-month rats stimulate the proliferation of lymphocytes to a significantly higher degree than do nucleopeptides from 28-month old rats. The experiments therefore identify in all three cell populations an age-related defect in antigen uptake and in metabolism of antigen to bioactive nucleopeptides, and they demonstrate that the nonparenchymal cells are more effective in antigen retention and in metabolism of antigen to nucleopeptides than are parenchymal cells. Further, the experiments support the thesis that the liver must be considered to be a principal part of the total immune system, its role much more fundamental than heretofore recognized.

Mechanism of immune transfer by RNA extracts. Immune RNA induces the synthesis of idiotype-bearing antigen receptors in noncommitted cells

Immune RNA (I-RNA) was extracted form lymphoid organs of BALB/c mice immunized with AKR lymphoid cells. Incubation of normal BALB/c spleen cells with this I-RNA (but not with normal RNA) resulted in leukocyte migration inhibition reactions (LMIR) against AKR extracts but not against purified protein derivative or BALB/c sarcoma extracts. This transfer was abolished by pretreating I-RNA with RNAse but not with pronase. The active fraction of I-RNA was retained by and could be eluted from Poly-U Sepharose columns. Normal cells pretreated with I-RNA also reacted in the presence of an anti-idiotypic anti-serum of anti-(BALB/c anti-AKR) specificity. Pretreatment of cells with anti-idiotypic serum plus complement did not inhibit the subsequent transfer of LMIR with I-RNA. Idiotypic receptors were expressed on I-RNA treated cells less than one hour after I-RNA treatment. Using an I-RNA of double specificity, the results suggested that I-RNA entered into and acted on the cells through a nonspecific mechanism. Finally, I-RNA could induce BALB/c anti-AKR idiotypic markers in C57Bl/6 cells, genetically committed for different idiotypes, while RNA extracted from C57Bl/6 immune cells could not induce in BALB/c cells their own genetically acquired idiotypes. This series of data would prove that I-RNA acting as a mRNA is able to induce in normal noncommitted cells the de novo synthesis of antigen receptors similar or identical to those present in the surface of in vivo immunized lymphoid cells of the same strain.

Antigen handling in relation to ageing

The distribution of a soluble antigen, 3H-BSA was studied in tissues (blood, liver, spleen, kidneys, lymph nodes, thymus and lungs) after intravenous injection into cohorts of the Fischer-344 rat colony of the National Institute on Aging that is maintained at Charles River Breeding Laboratories. The ten groups for which results are reported were maintained during the experimental procedures as the cohorts received from the "colony". Both the primary and secondary antigen injection were administered as 1 mg of protein per 50 g body weight. All the highly vascularized tissues of those studied showed the same relative distribution of antigen with age as the blood; i.e. a lower percentage of the injection at both extremes of the age span studied, 2 and 24 months of age. These age-related differences are more pronounced with primary than secondary immunization. Because of the higher level of antigen in the liver than blood, it is concluded that a specific localization of antigen occurs in the liver. Products of in vivo metabolism of 3H-BSA are isolated as liver nucleopeptides and are also co-isolated with liver polysomes. These particular forms of metabolized antigen have been shown to be immunogenic in other studies. The co-isolated polysome antigen in the present findings is reduced quantitatively in the older rats (for example, in 24 months compared to 12 month). The study of the changes in antigen parceling at the cellular and subcellular level, which occurs with ageing, is likely to provide insight into antigen induction.