THE manufacture of predefined specific antibodies by means of permanent tissue culture cell lines is of general interest. There are at present a considerable number of permanent cultures of myeloma cells1,2 and screening procedures have been used to reveal antibody activity in some of them. This, however, is not a satisfactory source of monoclonal antibodies of predefined specificity. We describe here the derivation of a number of tissue culture cell lines which secrete anti-sheep red blood cell (SRBC) antibodies. The cell lines are made by fusion of a mouse myeloma and mouse spleen cells from an immunised donor. To understand the expression and interactions of the Ig chains from the parental lines, fusion experiments between two known mouse myeloma lines were carried out.

Continuous cultures of fused cells secreting antibody of predefined specificity

For many years immunologists have been well served by the viewpoint that the immune system's primary goal is to discriminate between self and non-self. I believe that it is time to change viewpoints and, in this essay, I discuss the possibility that the immune system does not care about self and non-self, that its primary driving force is the need to detect and protect against danger, and that it does not do the job alone, but receives positive and negative communications from an extended network of other bodily tissues.

/pdf/tolerance-danger-and-the-extended-family-1qfdhdej1x.pdf

Tolerance, danger, and the extended family.

For over 50 years immunologists have based their thoughts, experiments, and clinical treatments on the idea that the immune system functions by making a distinction between self and nonself. Although this paradigm has often served us well, years of detailed examination have revealed a number of inherent problems. This Viewpoint outlines a model of immunity based on the idea that the immune system is more concerned with entities that do damage than with those that are foreign.

/pdf/the-danger-model-a-renewed-sense-of-self-329soztfh4.pdf

The Danger Model: A Renewed Sense of Self

In the genome of a germ-line cell, the genetic information for an immunoglobulin polypeptide chain is contained in multiple gene segments scattered along a chromosome. During the development of bone marrow-derived lymphocytes, these gene segments are assembled by recombination which leads to the formation of a complete gene. In addition, mutations are somatically introduced at a high rate into the amino-terminal region. Both somatic recombination and mutation contribute greatly to an increase in the diversity of antibody synthesized by a single organism.

Somatic generation of antibody diversity

The four distinct T-cell antigen receptor polypeptides (alpha, beta, gamma, delta) form two different heterodimers (alpha:beta and gamma:delta) that are very similar to immunoglobulins in primary sequence, gene organization and modes of rearrangement. Whereas antibodies have both soluble and membrane forms that can bind to antigens alone, T-cell receptors exist only on cell surfaces and recognize antigen fragments only when they are embedded in major histocompatibility complex (MHC) molecules. Patterns of diversity in T-cell receptor genes together with structural features of immunoglobulin and MHC molecules suggest a model for how this recognition might occur. This view of T-cell recognition has implications for how the receptors might be selected in the thymus and how they (and immunoglobulins) may have arisen during evolution.

T-cell antigen receptor genes and T-cell recognition.

Towards a network theory of the immune system.

Distinct plaques, each of which is due to the release of hemolysin by a single antibody-forming cell, are revealed by complement after incubation, in an agar layer, of a mixture of sheep red cells and lymphoid cells from a rabbit immunized with sheep red cells.

http://science.sciencemag.org/content/sci/140/3565/405.1.full.pdf

Plaque Formation in Agar by Single Antibody-Producing Cells

Antibody specificity is determined by structural v-genes that code for the amino acid sequences of the variable regions of antibody polypeptide chains. The present hypothesis proposes that the germ-cells of an animal carry a set of v-genes determining the combining sites of antibodies directed against a complete set of a certain class of histocompatibility antigens of the species to which this animal belongs. The evolutionary development of this set of v-genes in phylogeny is traced back to the requirements for cell to cell recognition in all metazoa. The hypothesis leads to a distinction between two populations of antigen-sensitive cells. One population consists of cells forming antibodies against foreign antigens; these lymphocytes have arisen as mutants in clones descending from lymphocytic stem cells which expressed v-genes belonging to the subset (subset S) coding for antibody against histocompatibility antigens that the individual happens to possess. The other population consists of allograft rejecting lymphocytes that express v-genes of the remaining subset (subset A) coding for antibody against histocompatibility antigens of the species that the individual does not possess. The primary lymphoid organs are viewed as mutant-breeding organs. In these organs (e. g. in the thymus), the proliferation of lymphocytes expressing the v-genes of subset S and the subsequent suppression of the cells of these “forbidden” clones, leads to the selection of mutant cells expressing v-genes that have been modified by spontaneous random somatic mutation. This process generates self-tolerance as well as a diverse population of antigen-sensitive cells that reflects antibody diversity. The proliferation in the primary lymphoid organs of lymphocytes expressing v-genes of subset A generates the antigen-sensitive cell population that is responsible for allo-aggression.



The theory explains how a functional immune system can develop through a selection pressure exerted by self-antigens, starting during a period in early ontogeny that precedes clonal selection by foreign antigens. The hypothesis provides explanations for the variability of the N-terminal regions of antibody polypeptide chains, for the dominant genetic control of specific immune responsiveness by histocompatibility alleles, for the relative preponderance of antigen-sensitive cells directed against allogeneic histocompatibility antigens, for antibody-idiotypes, for allelic exclusion, for the precommitment of any given antigen-sensitive lymphocyte to form antibodies of only one molecular species and for the cellular dynamics in the primary lymphoid tissues.

The somatic generation of immune recognition.

An immense amount of experimental data related to the problem of antibody formation has accumulated. Theories offering a basic interpretation of these observations have, in contrast, been few. The theory formulated in the present paper, though highly speculative, attempts to provide a framework for the interpretation of the main features of antibody appearance in response to the injection of antigen into an animal. 

Two views concerning the mechanism of antibody formation are at present most widely favored. One is the "antigen-template" theory, developed by Breinl [1], Haurowitz [1,2], Mudd [3], Alexander [4], and Pauling [5]. This theory assumes that antibodies can be produced only by cells in which the antigen is present. The specific affinity of an antibody molecule toward the antigen is due to a complementarity in structure derived from the folding of part of the polypeptide chain of a globulin molecule in direct contact with a determinant or haptenic region of the antigen. The antigen thus serves as a template in the final stage of formation of a globulin molecule. 

The other view tries to establish a similarity between antibody formation and adaptive enzyme formation and allows for the continued production of antibody after the antigen has disappeared from the body. This is the "modified-enzyme" theory, formulated by Burnet [6,7] and Fenner [7]. They propose that the introduction of an antigen into cells, containing enzymes directed toward the disposal of effete cells and cellular debris from the organism itself, induces the formation of "enzymic units" adapted toward the destruction of the antigen. A renewed contact with the antigen stimulates the replication of these enzymic units. Circulating antibody molecules are partial replicas of the modified enzymic units, carrying specificity but lacking enzymic action. 

The "natural-selection" theory, proposed in the present paper, may be stated as follows: The role of the antigen is neither that of a template nor that of an enzyme modifier. The antigen is solely a selective carrier of spontaneously circulating antibody to a system of cells which can reproduce this antibody. Globulin molecules are continuously being synthesized in an enormous variety of different configurations. Among the population of circulating globulin molecules there will, spontaneously, be fractions possessing affinity toward any antigen to which the animal can respond. These are the so-called "natural" antibodies. The introduction of an antigen into the blood or into the lymph leads to the selective attachment to the antigen surface of those globulin molecules which happen to have a complementary configuration. The antigen carrying these molecules may then be engulfed by a phagocytic cell. When the globulin molecules thus brought into a cell have been dissociated from the surface of the antigen, the antigen has accomplished its role and can be eliminated.

https://www.pnas.org/content/pnas/41/11/849.full.pdf

The natural-selection theory of antibody formation.

The preceding section implies that the immune system (like the brain) reflects first ourselves, then produces a reflection of this reflection, and that subsequently it reflects the outside world: a hall of mirrors. The second mirror images (i.e., stable anti-idiotypic elements) may well be more complex than the first images (i.e., anti-self). Both give rise to distortions (e.g., mutations, gene rearrangements) permitting the recognition of nonself. The mirror images of the outside world, however, do not have permanency in the genome. Every individual must start with self. Paraphrasing Nicolas Schoffer (Schoffer 1982): those who always seek exterior pressures (e.g., microbes) to account for the evolution of the sets of V genes, would do well to turn their vision towards the interiors of themselves, and there discover the mystery, perhaps never completely revealable, of the immune system.

Niels K. Jerne

Papers

Towards a network theory of the immune system.

Plaque Formation in Agar by Single Antibody-Producing Cells

The somatic generation of immune recognition.

The natural-selection theory of antibody formation.

Idiotypic networks and other preconceived ideas.