W. Braun

P. H. Hofschneider

W. Arber

W. Henle

N. K. Jerne

P. Koldovský

H. Koprowski

O. Maaløe

R. Rott

H. G. Schweiger

M. Sela

P. K. Vogt

R. Haas

E. Wecker

L. Svru?ek

The expression of many bacterial genes adapts itself in an almost in stantaneous and reversible way to specific environmental changes. More specifically, the concentration of a number of metabolites, a function of the amounts of enzymes involved in their synthesis or degradation, in turn retroacts on the rate of synthesis of these enzymes. The genetic bases for this regulation were established by JACOB and MONOD (1961). These authors also showed how the known elements of these regulatory mechanisms could be connected into a wide variety of circuits endowed with any desired degree of stability, in order to account for essentially irreversible processes like differentiation (MONOD and JACOB, 1961). The general principles used by JACOB and MONOD in their study of negative regulation were extended to positive regulation by ENGLESBERG et al. (1965). An independent approach permitted the discovery of positive controls in temperate bacteriophages (see below, III). Each control operation is mediated by a pair of complementary genetic elements (hereafter called "control cell"): a control gene which produces a l control (or regulator) protein and a control site which is the target for the regulator protein. Negative control means that the control protein (repressor) prevents gene expression. One deals with positive control when the control protein (activator) is necessary for this expression. It has become apparent that, as initially postulated by JACOB and MONOD, control of gene expression operates, at least to a large extent, at the transcriptional level.

Current Topics in Microbiology and Immunology / Ergebnisse der Mikrobiologie und Immunitätsforschung

L. Syru?ek

F. Cramer

P. Koldovsky

H.-G. Schweiger

Current Topics in Microbiology and Immunology

This volume is dedicated to the memory of the late Professor WERNER BRAUN, one of the most devoted and active members of the Editorial Board of the Current Topics in Microbiology and Immunology, who passed away, after suffering a heart attack, in November 1972. Dr. WERNER BRAUN was born in Berlin, Germany, on November 16,1914. During his highschool days in Berlin he did research work on problems of genetics as a young guest in the Kaiser-Wilhelm-Institut fur Biologie, in the department of Prof. R. GOLDSCHMIDT. I remember his colourful description of his discussions during this period, while still a teen-ager, with OTTO WAR BURG. He studied biology and medicine at the University of G6ttingen and received a Ph.D. degree in biology in 1936. In the same year he left Nazi Germany and came to the United States first as a Guest Investigator in Genetics at the University of Michigan at Ann Arbor, and then in Berkeley, where he carried out his work in the Depart ments of Zoology and of Veterinary Science until 1948. He was engaged during this period in the study of problems concerned with physiological genetics, bacterial variation, immunology and biochemistry.

J. H. Humphrey

Volume 65

Volume 68

Expression of an immune response is the net result of complex synergisƯ tic and antagonistic activities performed by a variety of cell types. It includes macrophages, T and B populations which may interact in performance of a response, and suppressor cells interfering with it. Accordingly, a lack of resƯ ponse may not necessarily indicate absence of immunocompetent cells, but rather nonexpression of competence. Thus, one should consider two possible situations, which are by no means mutually exclusive, to account for immunoƯ logic unresponsiveness: (a) one or more of the cell populations composing the synergistic unit is absent or immature, and (b) an antagonistic unit which interferes with the response is dominating. In view of this, an approach to development of immune reactivity necessitates parallel surveys of development of cells with the potential to perform, as well as of cells which can suppress the response. Classification of the various cell types has been based so far on their phenotypic properties (e. g., membrane antigen markers, cell receptors, proƯ duction and secretion of immunoglobulins, etc.). Genotypically, T and B cells may represent either separate, independent cell lines, or different stages of development within the same cell lineage.

Volume 73

M. Sela

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