In vitro studies of immunological responses of lymphoid cells

Immune modulators with defined molecular targets: cornerstone to optimize rational vaccine design

Vaccination remains the most valuable tool for preventing infectious diseases. However, the performance of many existing vaccines should be improved and there are diseases for which vaccines are still not available. The use of well-defined antigens for the generation of subunit vaccines has led to products with an improved safety profile. However, purified antigens are usually poorly immunogenic, making essential the use of adjuvants. Despite the fact that adjuvants have been used to increase the immunogenicity of vaccines for more than 70 years, only a handful has been licensed for human use (e.g., aluminium salts, the micro-fluidized squalene-in-water emulsion MF59 and monophosphoryl lipid A). Thus, the development of new adjuvants which are able to promote broad and sustained immune responses at systemic and mucosal levels still remains as a major challenge in vaccinology. Recent advances in our understanding of the immune system have facilitated the identification of new biological targets for screening programs aimed at the discovery of novel immune stimulators. This resulted in the identification of new candidate adjuvants, which made possible the modulation of the immune responses elicited according to specific needs. A number of promising adjuvants which are currently under preclinical or clinical development will be described in this chapter.

The interface between innate and adaptive immunity

This focus analyzes some of the ways the innate immune system influences adaptive immune responses. Here the main principles and themes that govern this intricate relationship are discussed.

The dynamics of conceptual change in twentieth century immunology

I have attempted here to define three distinct eras in the 110-year history of the discipline of immunology. The first, extending from 1880 to about the First World War, centered around the new bacteriology and infectious diseases, and had a distinctly medical orientation. Several of the components of the original research program in immunology failed to maintain their original momentum or to fulfill their initial high promise, and went into decline. These include the development of new vaccines, serotherapeutic approaches, the study of cellular immunity, and the study of diseases that might be mediated by cytotoxic antibodies. Two other subprograms followed a somewhat different course; the study of anaphylaxis and related diseases passed primarily into the hands of clinical allergists, while the development and adaptation of serodiagnostic techniques passed into the hands of the new discipline of serology, both fields out of the mainstream of post-World War I immunology. As interest in the components of the old program was falling away, there developed a new area of interest in immunology. Leadership in the field devolved upon a new group of individuals with a predominantly chemical orientation to the study of antigens and antibodies, who pursued a research program and developed a theoretical base that reflected this orientation well. It may be interesting to examine more closely the forces responsible for this shift in emphasis. When interest in the old areas waned, the medically oriented practitioners did not switch to more immunochemical lines, but went in other directions. Karl Landsteiner was the only prominent "old-timer" who contributed significantly to the newer immunology, and it was his work that set the tone and attracted the new generation of immunochemists who became the reigning Denkkollektiv. A science does not change its precepts and approaches spontaneously; it is moved to the new position by those who explore fertile new areas. This is not to say, however, that there was no longer interesting and important work to be done along the old lines--it was just that such work was no longer "fashionable", as the reception of the work of Dienes, of Rich, of Rivers, and of the early Medawar illustrates. Whereas the earlier immunological program had interacted extensively with many different fields of biology and medicine, the immunochemical era was characterized by a relative introversion, as compared with the broad influence exerted by the earlier immunological program (92). We can date this second era from about the First World War until the late 1950s and early 1960s.(ABSTRACT TRUNCATED AT 400 WORDS)

Characterization of human lymphocytes which proliferate "spontaneously" in vitro

Human peripheral blood lymphocytes proliferate "spontaneously" in vitro following the reduction in the proportion of monocytes in culture. This cell proliferation, which takes place in the absence of any extrinsic antigenic stimulation, was found to reside in a small fraction of a non-T non-B cell population which was also Fc receptor-negative. Concomitant with the in vitro proliferation of the monocyte-depleted cells, an increase in the proportion of E rosette-forming cells was observed. Hence, in addition to the regulation of spontaneous proliferation of lymphocytes, it is suggested that monocytes may also be involved in the regulation of the proportion of T cells or in expression of the E-rosetting marker.

Cytochalasin B inhibits lymphotoxin production by antigen-stimulated lymphocytes

Lymph node cells of rats sensitized with hen ovalbumin produced lymphotoxin after 6 to 12 hours of exposure to specific antigen. Lymphotoxin was assayed by its cytotoxicity for fibroblasts from syngeneic embryos during a 72-hour incubation. Cytochalasin B inhibited lymphotoxin production, as well as later DNA synthesis, at concentrations (0.1 to 5.0 micrograms per milliliter) comparable to those which affect microfilament function and cell motility in other systems, and this inhibition was reversible. Binding of antigen was not affected.

Immune response to gluten in adult coeliac disease

Cultures of mesenteric node lymphocytes obtained from two adult coeliac disease patients were stimulated by gluten fraction III. No stimulation was observed in cultures of axillary node lymphocytes from one of these patients, of mesenteric node lymphocytes from the two patients with other diseases or of peripheral blood lymphocytes from adult coeliacs and normal subjects. Peripheral blood lymphocytes of two of the six adult coeliac patients responded poorly to phytohaemagglutin alone, but this was probably owing to technical factors. In a further six adult coeliacs skin tests to gluten fraction III were negative. It is suggested that delayed hypersensitivity to gluten is likely to have a secondary pathogenic role in adult coeliac disease.

Cells involved in the immune response. IV. The response of normal and immune rabbit bone marrow and lymphoid tissue lymphocytes to antigens in vitro

Cell suspensions of immune rabbit lymph nodes and spleen were capable of undergoing blastogenesis and mitosis and of incorporating tritiated thymidine when maintained in culture with the specific antigen in vitro. They did not respond to other, non-cross-reacting antigens. The blastogenic response obtained with immune lymph node cells could be correlated with the antibody synthesizing capacity of fragment cultures prepared from the same lymph nodes. Cell suspensions of immune bone marrow responded to non-cross-reacting antigens only whereas cell suspensions of immune thymus, sacculus rotundus, and appendix did not respond when exposed to any of the antigens tested. On the other hand, neither fragments nor cell suspensions prepared from lymph nodes, spleen, and thymus of normal, unimmunized rabbits responded with antibody formation and blastogenesis when exposed to any of the antigens. However, normal bone marrow cells responded with marked blastogenesis and tritiated thymidine uptake. The specificity of this in vitro bone marrow response was demonstrated by the fact that the injection of a protein antigen in vivo resulted in the loss of reactivity by the marrow cell to that particular antigen but not to the other, non-cross-reacting antigens. Furthermore, bone marrow cells of tolerant rabbits failed to respond to the specific antigen in vitro. It was also demonstrated that normal bone marrow cells incubated with antigen are capable of forming antibody which could be detected by the fluorescent antibody technique. This response of the bone marrow cells has been localized to the lymphocyte-rich fraction of the bone marrow. It is concluded that the bone marrow lymphocyte, by virtue of its capacity to react with blastogenesis and mitosis and with antibody formation upon initial exposure to the antigen, a capacity not possessed by lymphocytes of the other lymphoid organs, has a preeminent role in the sequence of cellular events culminating in antibody formation.

Cytotoxic action of stimulated lymphocytes on allogenic and autologous erythrocytes

Fowl erythrocytes are lysed when exposed to an excess of fowl blood lymphocytes in the presence of phytohemagglutinin. No significant cell damage is seen in the absence of phytohemagglutinin, or when the lymphocytes are replaced by malignant lymphoid cells, thymus cells, or nonlymphoid cells. The lymphocytes remain viable during the reaction. Differences in histocompatibility between lymphocytes and erythrocytes are not required. Autologous lymphocytes are cytotoxic to the same extent as allogenic lymphocytes over a wide range of experimental conditions.

Uptake of protein by mammalian cells: an underdeveloped area. The penetration of foreign proteins into mammalian cells can be measured and their functions explored

Although it is accepted on the basis of biological and morphological evidence that mammalian cells will take up macromolecules, little is known about the kinetics, the specificity, and the functions of this uptake. With labeled proteins used as models, it is found that the transport proceeds at very low rates, requires little energy, and is markedly enhanced by polybasic compounds. Molecular charge and size are important factors: cells clearly favor cationic macromolecules of large molecular weights. Neither factor, however, can fully account for the selectivity detected in the uptake of different proteins. Ingested albumin undergoes rapid and extensive degradation. This fact suggests that macromolecules have only a limited chance to express their biological activity in target cells, a finding that is relevant also to the role of foreign nucleic acids and the possibility of achieving genetic transformation in animal cells. There are concrete indications, however, that in spite of their short half-life, proteins can act as carriers, as precursors of active agents, and as regulators of metabolic functions in host cells. They may also be important in the control of growth and differentiation. These functions of exogenous proteins are still largely unexplored.