Jerne's success in developing the plaque-forming cell methodology for determining the number of specific antibody-producing lymphocytes during the immune response has prompted scientists to calculate the number of antibody molecules produced by a single cell. In this article, calculations of the rate of antibody production are made, and a special attention is called to the number of ribosomes in a cell, the rate of protein chain elongation and various other parameters. The generally accepted notion of 2000 IgM molecules or some 15,000 IgG molecules per second (per cell) remains an acceptable estimate. The article describes the work of Ivan Lefkovits and the interaction among research groups leading to quantitative evaluations of the components of the immune system.

Jerne's success in developing the plaque‐forming cell methodology for determining the number of specific antibody‐producing lymphocytes during the immune response has prompted scientists to calculate the number of antibody molecules produced by a single cell. In this article, calculations of the rate of antibody production are made, and a special attention is called to the number of ribosomes in a cell, the rate of protein chain elongation and various other parameters. The generally accepted notion of 2000 IgM molecules or some 15,000 IgG molecules per second (per cell) remains an acceptable estimate. The article describes the work of Ivan Lefkovits and the interaction among research groups leading to quantitative evaluations of the components of the immune system.

A phase 1 trial of a candidate human immunodeficiency virus type 1 (HIV-1) vaccine was done in 25 healthy seronegative subjects. The antigen, env2-3 (SF2), was a nonglycosylated polypeptide representing the gp120 region of the env gene of the HIV-1(SF2) isolate. It was produced in genetically engineered yeast as a denatured molecule incapable of binding CD4. A synthetic lipophilic muramyl tripeptide (MTP-PE) was used as an adjuvant. Ten subjects received adjuvant alone and 15 received 50- or 250-micrograms doses of env2-3 (SF2) administered intramuscularly in two immunization regimens. In general, adjuvant and vaccine were well tolerated. Antibody responses to both the homologous antigen, env2-3 (SF2), and antigens from other highly divergent HIV isolates were elicited in the majority of vaccine recipients. However, antibody titers were low, without neutralizing activity. In 9 of 11 subjects who received the complete vaccine immunization series, a significant specific T lymphocyte response was observed.

A nonglycosylated denatured form of human immunodeficiency virus (HIV) 1 glycoprotein gp120 (Env 2-3), which does not bind to CD4, was used with muramyl tripeptide as adjuvant to immunize HIV-seronegative healthy volunteers. In all the volunteers, three 50-micrograms injections of Env 2-3 induced priming of CD4+ T cells specific for conserved regions of the native glycosylated gp120. Moreover, we found that several major histocompatibility complex class II (DR) alleles can function as restriction molecules for presentation of conserved epitopes of gp120 to T cells, implying that a T-cell response to these epitopes can be obtained in a large fraction of the population. The possibility to prime CD4+ T cells specific for conserved epitopes of a HIV protein is particularly important in view of the lack of such cells in HIV-infected individuals and of a possible role that CD4+ T cells may play in the development of protective immunity against AIDS.

T cells are activated physiologically by triggering the T-cell receptor-CD3 complex. There is evidence that invariant accessory molecules on the T-cell membrane (CD8 and CD4) are involved in the major histocompatibility complex-restricted recognition process. Moreover, binding and crosslinking of these accessory molecules to the T-cell receptor-CD3 complex exerts a positive synergistic signal, as has been shown by stimulation with crosslinked antibodies. Here we demonstrate that stimulation mediated by immobilized anti-CD3/CD8 antibodies differs from stimulation mediated solely by anti-CD3. Whereas interleukin 2 receptor expression and interferon gamma production are seen to a similar extent in both cases, a second signal provided by the additional involvement of CD8 seems to be essential for interleukin 2 production and full interleukin 2 responsiveness in CD8+ T cells. This second signal is much more sensitive to inhibition by 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine, an inhibitor of protein kinase C and cGMP/cAMP-dependent kinases. Our results also show that substantial modulation of the T-cell receptor complex and most likely CD3 phosphorylation are not essential for initiating the activation of resting T cells. Instead, we found a 22- to 24-kDa phosphoprotein whose strong phosphorylation correlated reliably with T-cell activation.

Since its introduction in 1979 protein blotting has become a routine tool in research laboratories. In the clinical laboratory its potential is becoming recognised for applications in fields such as infectious and autoimmune diseases, allergy and others. In this article we would like to outline the basic principles of protein blotting, to illustrate these with some examples related to clinical applications and to point out differences between these and classical methods.

The most abundant inhibitory neurotransmitter in the central nervous system, gamma-aminobutyric acid (GABA), exerts its main effects via a GABAA receptor that gates a chloride channel in the subsynaptic membrane. These receptors can contain a modulatory unit, the benzodiazepine receptor, through which ligands of different chemical classes can increase or decrease GABAA receptor function. We have now visualized a GABAA receptor in mammalian brain using monoclonal antibodies. The protein complex recognized by the antibodies contained high- and low-affinity binding sites for GABA as well as binding sites for benzodiazepines, indicative of a GABAA receptor functionally associated with benzodiazepine receptors. As the pattern of brain immunoreactivity corresponds to the autoradiographical distribution of benzodiazepine binding sites, most benzodiazepine receptors seem to be part of GABAA receptors. Two constituent proteins were identified immunologically. Because the monoclonal antibodies cross-react with human brain, they provide a means for elucidating those CNS disorders which may be linked to a dysfunction of a GABAA receptor.

Monoclonal antibodies (mAb) against a gamma-aminobutyric acid/benzodiazepine receptor complex (GABAA/BZR) were produced by using spleen cells from a mouse immunized with GABAA/BZR purified from bovine cerebral cortex. The mAb, most of which were of the IgG1 isotype could be divided into four groups (I-IV) specifying different antigenic structures. On immunoblots, group I mAb recognized exclusively the Mr 55,000 beta-subunit, while groups II and IV mAb recognized the Mr 50,000 alpha-subunit of bovine GABAA/BZR. Three of the four groups of mAb (I, III, and IV) crossreacted with both human and rat GABAA/BZR with the same subunit specificity as in bovine brain; the fourth group (II) crossreacted with human but not with the rat receptor. The binding sites for benzodiazepines as well as the high and low affinity GABA sites reside on the same structural complex as shown by immunoprecipitation. Ligand binding to these sites was not inhibited by mAb. Since quantitative immunoprecipitation of GABAA/BZR was achieved with mAb selective for either the alpha- or beta-subunit, both subunits occur in each individual receptor complex. The pattern of immunoblot staining suggests that the smaller alpha-subunit is not a processing product of the larger beta-subunit. Both alpha- and beta-subunits were present in all brain areas and species tested (rat cerebral cortex, cerebellum, and hippocampus; bovine cerebral cortex and cerebellum; human cerebral cortex). This suggests a uniform subunit composition of the receptor throughout the brain in contrast to earlier evidence for a heterogeneous subunit composition based on photoaffinity labeling.

A mouse monoclonal antibody (mAB lu-5) was prepared using a lung cancer cell line as an antigen. The selected clone produces an IgG with a gamma-1 heavy chain and a kappa-light-chain. Immunohistochemical testing of mAB lu-5 on 117 normal tissue biopsies and 474 tumours revealed reactivity with an intracytoplasmic, formaldehyderesistant antigen present in most epithelial and mesothelial cells, but absent in mesenchymal cells. The antibody can therefore be used as a first order, pan-epithelial marker. It proved also useful for fast tumour diagnosis on frozen sections.

Binding of the Met-tRNAMetf . eIf-2 GTP complex to the 40 S ribosomal subunit is the first step in initiation of eukaryotic protein synthesis. The extent of binding and the stability of the complex are enhanced by initiation factors eIF-3 and eIF-4C, AUG and elevated magnesium concentration. The reversibility of reaction steps occurring during the assembly of the initiation complex is measured as the rate of Met-tRNAMetf exchange in the initiation complex and its intermediates. This rate progressively decreases and Met-tRNAMetf binding becomes irreversible upon binding of mRNA. The association of the 40 S Met-tRNAMetf mRNA initiation complex with the 60 S ribosomal subunit is again reversible as long as elongation does not occur.

This chapter discusses the distinction of epitopes by monoclonal antibodies. The chapter explains that hybridoma technology has become very efficient in the production of large numbers of specific monoclonal antibodies. The chapter describes in detail three main methods for the distinction of specificity of different mAb: competition solid phase antibody binding assay (SABA) binding to epitopes on different molecules and epitope destruction by iodination. Competition SABA is a generally applicable method based on the assumption that two mAb can bind to one antigen molecule simultaneously if they bind to different epitopes. In addition, different methods are discussed by which mAb-2 is measured selectively in the presence of mAb-1. The chapter explains that the choice of method depends on several factors including convenient availability of different reagents.

This electron microscopic study demonstrates that formation of a functional eukaryotic 40S initiation complex is accompanied by conformational changes which obscure the characteristic structural features of the 40S ribosomal subunits and of the initiation factor eIF-3, the only macromolecular components of the complex individually resolvable by conventional high resolution electron microscopy. The complex, characterized by a sedimentation coefficient of 46S, appears as a globular particle with a diameter of about 280 A and several characteristic protrusions and incisions. Similar structures were obtained with [40S X eIF-3] initiation complexes formed by interaction of eIF-3 from rabbit reticulocytes with 40S ribosomal subunits from either A. salina cysts or mouse liver. Incubation of eIF-3 with prokaryotic 30S subunits from E. coli produced no [30S X eIF-3] structures. The binding of eIF-3 to 40S subunits is weak, and both the [40S X eIF-3] and the complete 40S initiation complexes have to be stabilized by glutaraldehyde fixation. The extensive conformational changes associated with the complex formation preclude direct electron microscopic localization of eIF-3, a globular protein approximately 100 A in diameter, in the initiation domain of the 40S subunit.

This chapter explains spleen cell analysis and optimal immunization for high-frequency production of specific hybridomas. By size analysis of the spleen cells, it is possible to measure directly the increase of the numbers of blast cells in the spleen of an immunized mouse over the background levels. The chapter also discusses specific efficiency (SE) and counting of hybridomas. A hybridization experiment is successful if one obtains many hybrids and if a high proportion of these hybrids secretes specific antibodies. The methods described in this chapter have a bearing only on the proportion of specific hybrids on specific efficiency (SE).

Antiviral activity of recombinant human leukocyte A interferon was inactivated by heating at 65 degrees C or by reduction of disulfide bonds. The specific immunoreactivity, as measured by radioimmunoassays measuring binding to monoclonal antibodies, decreased concomitantly with the antiviral activity. Although the monoclonal antibodies did bind to inactivated interferon, their binding affinity to inactivated interferon was in general very much lower than their binding affinity to active interferon. Therefore, this immunoassay could replace the antiviral assay for detection of biologically active interferon. In addition, most of these antibodies should be especially useful for purification of the interferons since they discriminate between the native active and inactive denatured species. Screening for such antibodies is convenient and simple. The general use of antibodies that preferentially interact with native molecules provides a powerful new principle for choosing monoclonal antibodies with extraordinary potential in assay and purification.

A stable complex between 18 S rRNA and globin mRNA has been isolated from 40 S initiation complexes in the reconstituted reticulocyte cell free system. This complex is only formed under the conditions which also lead to an initiation complex active in protein synthesis. The mRNA-18 S rRNA interaction has properties compatible with base-pairing. This observation is discussed in the context with other, in part controversial, observations relating to base pairing as a step in initiation of eukaryotic protein synthesis.