Ruth Lifshitz

Linkage of murine (T,G)-A--L-specific idiotypic determinants to the heavy chain constant region allotypic markers.

We have previously reported the production in guinea pigs of anti-idiotypic antibodies against (T,G)-A--L-specific antibodies of high responder C3H.SW (H-2 b, Igh-1 a, Herzenberg and Herzenberg 1978), mice (Schwartz et al. 1978). The guinea pig antisera possessed anti-idiotypic antibodies which reacted with bindingsite associated determinants (Schwartz et al. 1978). Immunization with either the closely related antigen (Phe, G)-A--L or with (T,G)-A--L complexed with methylated bovine seicum albumin (MBSA) led to the production of (T,G)-A--L-specific antibodies which possess cross-reactive idiotypes with C3H.SW anti-(T,G)-A--L antibodies (Schwartz et al. 1978, Lifshitz et al. 1978). A limited strain survey suggested a linkage between the expression of idiotypic determinants and the heavy chain constant region Igh-1 a allotypic locus of the mouse (Schwartz et al. 1978). This suggestion was confirmed when (T,G)-A-L specific antibodies of the two congenic strains C3H.SW (H-2 b, Igh-1 a) and CWB (H-2 b, Igh-I b), which differ only in the Igh1 allotypic complex, were tested. We have demonstrated that, whereas the binding of 125 I-C3H.SW anti-(T,G)-A-L antibodies (idiotypes) to guinea pig anti-idiotypic sera was completely inhibited by the homologous antibodies, no inhibition was obtained by excess of CWB anti-(T,G)-A--L antibodies (Schwartz et al. 1978). In the present report we have broadened the number of strains screened for idiotypic expression utilizing (Phe, G)-A--L to which most of the mouse strains respond with the production of (T,G)-A-L-specific antibodies. In addition, genetic analysis was performed in the segregating backcross population between F 1 hybrids of C3H.SW (idiotype +) and CWB (idiotype-) and the CWB parental mice for establishing the suggested linkage between the expression of the inherited idiotypic determinants and the Igh-I ~ allotype.

Comparative analysis of native and cysteine-deficient HIV-1 reverse transcriptase.

To study the subunit structure and the active site of human immunodeficiency virus reverse transcriptase (RT), the enzyme was expressed in E. coli and purified to homogeneity in large quantities. The recombinant enzyme consists of two major polypeptides of 66,000 and 53,000 Da in equimolar amounts and a minor species of 51,000 Da. Amino acid sequence analysis of the recombinant proteins revealed that the amino termini of the two major subunits are identical to that of the virion-derived enzyme. The two cysteinyl residues at positions 38 and 280 in the RT amino acid sequence were replaced by alanine in an attempt to elucidate the role of the sulfhydryl groups in RT enzyme activities, heterodimer formation, and intrasubunit linkage. The results reported here show that the two cysteinyls are dispensable and their absence in the amino acid sequence of the reverse transcriptase does not affect DNA polymerase or ribonuclease H enzyme activities or the formation of heterodimer structures. Furthermore, inhibitors of polymerase activity such as 3-azidothymidine triphosphate, dideoxythymidine triphosphate, and tetrahydroimidazo[4,5,1-JK][1,4]benzodiazepens (1H)-one are equally effective on the mutant containing no cysteinyl residues and the wild-type enzyme.

Analysis of the T Cell Recognition System Using (T,G)-A--L Specific Helper T Cell Lines

The nature and cellular expression of immune response (Ir) genes have been the subject of extensive studies for more than a decade. One of the antigens which was widely used in studies aimed at the elucidation of the function and expression of Ir genes is the synthetic polypeptide poly(Tyr,Glu)-poly(DLAla)--poly(Lys), abbreviated as (T,G)- A--L (1–3). Using this antigen and closely related synthetic polypeptides, determinant specific genetic regulation was demonstrated (4,5), and it has been shown that Ir genes may be expressed on different cell types depending on the antigenic system and on the genetic constitution of the mouse strain studied (6–9). However, since different cell types are involved in the immune response, and as the biological systems used are complicated, different interpretations were often suggested for the same set of results, and thus the issue of the mode of regulation exerted by Ir genes has not been finally resolved yet. It is likely that the elucidation of the receptors of cells involved in the immune response will help in the understanding of the role and expression of Ir genes on these cells.