Cytodynamics of the immune response in two lines of mice genetically selected for "high" and "low" antibody synthesis.

Two lines of mice have been separated by selective breeding for the character "agglutinin production to heterologous erythrocytes." Around the 18th generation of selection the two lines could be considered as homozygous for the character investigated. This trait is under the control of a group of additive genes. The interline difference in the production of anti-SE agglutinins was verified for the range of antigen doses from subimmunogenic to maximal. After intravenous immunization with an optimal dose of SE, the duration of the exponential rise in serum antibody was 4-5 days in both lines. At this time most of the interline difference in responsiveness is already expressed. A cytodynamic study carried out in terms of plaque-forming cells (PFC) and rosette-forming cells (RFC) in the spleen during the exponential phase showed that the principal interline difference is found in the doubling time of cells engaged in the immune response. More precise cytodynamic analysis made in terms of RFC showed that the doubling time of RFC is 9 hr in high responder and 16 hr in low responder mice. The duration of the exponential rise and the number of target cells stimulated by antigen is the same in both lines. The interline difference at the end of the exponential rise (4 days postimmunization) is larger in terms of serum antibody (30-40-fold) than in terms of PFC or RFC (20- and 11-fold, respectively). A morphological study of RFC in nonimmunized mice showed that about 90% of rosettes were formed by small lymphocytes in both lines. The remainder were medium-sized lymphocytes. At the peak of the cellular response the RFC have differentiated into large lymphocytes, blast cells, and plasma cells. The contribution of plasma cells to RFC is much greater in the high than in the low line. The cytodynamic and morphologic results presented in this article are compatible with the hypothesis that the group of genes segregated in each line during the selective breeding control and regulate the rate of multiplication and differentiation of the antibody-producing cells.

Serum concentrations and allotypes of immunoglobulins in two lines of mice genetically selected for "high" or "low" antibody synthesis.

Random-bred Swiss mice were selectively bred for 16 generations; selection was based on their agglutinin response to sheep and pigeon erythrocytes to produce a high and a low responder line. The serum levels of individual immunoglobulins differed significantly in these two lines before immunization. The differences in the levels of immunoglobulins were much more marked after immunization with pigeon or sheep erythrocytes. Greater differences between the two lines were noted in IgM and IgG levels than in IgA. Another remarkable finding was the presence of different immunoglobulin phenotypes in the two lines. The high responders were homozygous or heterozygous for heavy-chain linkage groups found separately in the prototype BALB/c and C57BL inbred strains. The low responders were homozygous for a heavy-chain linkage group not present in bred mice in the United States, but observed as a recombinant type among wild mice probably representing a crossover between the heavy-chain linkage groups of the prototype DBA/2 and NH inbred mice.

Genetic control of macrophage functions. I. Polygenic regulation of phagocytosis stimulation produced by Glyceryl Trioleate.

The phagocytic index K, established from the rate of blood clearance of colloidal carbon, measures the phagocytic activity of RE macrophages in contact with the circulating blood. The intravenous injection of glyceryl trioleate (triolein) produces a marked stimulation of the phagocytic activity of RE macrophages. This response is higher in the female than in the male mice. The phenotypic character "responsiveness of macrophage to triolein" presents large individual variants in population of random bred albinos mice. This character is submitted to polygenic regulation. Starting from a foundation population of 25 males and 25 females random bred albinos, mice, two lines were separated by selective breeding for the character "responsiveness to triolein": a "high" responder line, KTH, and a "low" responder line, KTL. After 26 consecutive generations of selective breeding, KTH mice present a very high response to triolein while KTL mice are almost irresponsive. The heritability of this character (h2) calculated from the interline divergence is of 12% plus or minus 1. This value of h2 indicates that the character investigated is determined by the cumulative effect of a group of about 27 independently segregating loci. The distribution of the character in (KTH plus KTL)F1 and their backcrosses with parental lines suggests that low responsiveness is dominant over high responsiveness. The genetic regulation of responsiveness to triolein is independent from the dose administered. These results are discussed in relation to the importance of genetic factors controlling macrophage functions involved in lipid metabolism and in the specific mechanisms of immunity.

Genetic factors controlling anti-sheep erythrocyte antibody response and immunoglobulin synthesis in backcross and F2 progeny of mice genetically selected for "high" or "low" antibody synthesis.

Agglutinin responses to sheep erythrocytes and immunoglobulin heavy chain phenotypes determined in F(1), F(2), and backcross progeny of mice genetically selected for high and low antibody synthesis indicated that an immune response gene for sheep erythrocytes is linked to the immunoglobulin heavy chain allotype. Mice homozygous for the phenotype of the high line had significantly higher titers than mice homozygous for the phenotype of the low line. An association was also observed in some progeny of the backcross of the F(1) generation with the low line. However, the control of the immune response was clearly multigenic since heterozygous mice of the same phenotype (2/3, 5) resulting from the two backcrosses (high and low) had very different immune responses. Immunoglobulin levels in the same progeny showed no linkage to the immunoglobulin allotype but a rather simple pattern of inheritance.

Comparison of 7,12-dimethylbenz(a)anthracene-DNA adduction in the epidermis of two lines of mice selected for resistance (CAR-R) or susceptibility (CAR-S) to skin carcinogenesis.

Two lines of mice were produced by bidirectional selective breeding: one resistant (CAR-R) and one susceptible (CAR-S) to two-stage skin carcinogenesis by dimethylbenz(a)anthracene and 12-O-tetradecanoyl-phorbol-13-acetate. The dimethylbenz(a)anthracene-DNA adduct formation was compared in the two lines by a postlabeling procedure so as to determine whether the striking interline difference observed as to tumor incidence could (in part) be due to differences in the formation of DNA-reactive metabolites. Results show that qualitatively, adduct profiles in CAR-R and CAR-S epidermis are similar. Quantitatively, the total binding level is slightly higher in CAR-S versus CAR-R mice during the 30-day follow-up. However, these minor differences do not increase in function of the response to selection observed through three consecutive generations. A 2- or 4-week promotion with 12-O-tetradecanoylphorbol-13-acetate enhances the decrease of adduct level in the two lines. This effect is somewhat more pronounced in CAR-S mice. Results strongly suggest that the expression of the genes responsible for CAR-R/CAR-S phenotypic difference affects mainly the postinitiation stages.

Genetic control of immune responsiveness, aging and tumor incidence.

Age-related alterations of the immune system affect both antibody and cell-mediated immune responses, T-cell responses being more severely affected than B-cell responses. Within the T-cell population, aging leads to replacement of virgin by memory cells and to accumulation of cells with signal transduction defects. Changes in T-cell subsets and in cytokine production profiles may produce suitable conditions for T-cell-mediated disregulation of antibody responses characterized by the production of low affinity and self-reactive antibodies. Also B-cells exhibit intrinsic defects and natural killer (NK) cell activity a profound loss in old mice. Whether age-related immune disfunctions influence life span and tumor incidence has been examined in mice genetically selected for high or low antibody responsiveness. It has been found that genetic selection of vigorous antibody responses in most cases produces mice with longer life span and lower lymphoma incidence. Moreover, the results of genetic segregation experiments indicate that antibody responsiveness and life span are polygenic traits regulated by a small number of the same or closely linked loci. Mice genetically selected for high or low mitotic responsiveness to PHA exhibit low or high tumor incidence, respectively, but no difference in life span, suggesting that T-cell activity is restricted to immune surveillance of neoplastic transformation. Studies on mice genetically selected for resistance or sensitivity to chemical carcinogenesis have uncovered loci that control both resistance to tumor induction and longevity while have no effects on immunity and disease incidence. Thus, the relative role of the immune system in conditioning the duration and the biological quality of life remains to be determined.

Quantitative effect of H-2-linked gene(s) on antibody response to human gamma-globulin.

H-2-linked gene(s) have been found to play a role in the quantitative regulation of response to human gamma-globulin (HGG) in mice selected for high or low antibody responsiveness to sheep erythrocytes. Unexpectedly, in a random genetically heterogeneous population of F2 interline hybrids, the gene(s) linked to the H-2 phenotype of H mice has a "low" effect, and the gene(s) linked to the H-2 phenotype of L mice a "high" effect on the magnitude of antibody response to HGG. In H and L mice, the non-specific polygenic control of antibody responsiveness is able to compensate/counteract the inverse effect of HGG-specific H-2-linked gene(s) since the usual interline difference is observed.

Genetic regulation of the specific and non-specific component of immunity.

Bi-directional selective breeding for antibody (Ab) responsiveness to heterologous erythrocytes (Selection I) produced a high (H) and a low (L) responder line of mice which were also remarkably separated for Ab responses to many unrelated natural antigens (Ags) such as heterologous proteins, viruses, bacteria, parasites and haptens carried by these immunogens. The character "quantitative Ab responsiveness" is controlled by several independently segregating loci (polygenic regulation). The major genetic modification is produced at the level of macrophage activities. The Ag is slowly catabolized and persists for a long time on the macrophage membrane of the H line, whereas it is rapidly destroyed in L line macrophages. The bactericidal and bacteriostatic activity of the macrophage is also strong in the L line and weak in the H line. The opposite genetic regulation of Ab responsiveness and macrophage activity is a fundamental phenomenon for understanding natural and vaccination-induced anti-infectious immunity. The L line is more resistant than the H line against the infections due to intracellular microorganisms (Salmonellae, Yersinia, Mycobacteria, Brucellae, Leishmania) where the macrophage plays the dominant defensive barrier. The H line is more resistant than the L line to the extracellular microorganisms which are efficiently counteracted by a strong antibody response (Pneumococcus, Klebsiella, Plasmodia, Trypanosoma). The intensity of T cell-mediated immunity as measured by delayed type hypersensitivity, which is independent of the genetic regulation of antibody responsiveness, is correlated with the degree of nonspecific inflammation produced at the site of the reaction by the Ag injection in non-sensitized mice.(ABSTRACT TRUNCATED AT 250 WORDS)

Low antibody responsiveness is found to be associated with resistance to chemical skin tumorigenesis in several lines of Biozzi mice.

High and low antibody responder lines of mice from Selections I, III and G were assayed for two-step skin tumorigenesis using a protocol consisting in initiation with 7,12-dimethylbenz[a]anthracene (DMBA) and promotion with 12-O-tetradecanoylphorbol-13-acetate (TPA). Concordant results were obtained in the three selections: low antibody responder mice were shown to be significantly more resistant to tumor induction than the high responder counterparts. The difference was observed for all parameters: kinetics and percentages of tumor incidence and tumor multiplicity. The three bidirectional selective breeding experiments differed in several respects namely, the origin of the foundation populations, the antigens and immunization protocols used during the selection, as well as the breeding unit environments. Therefore, the consistent results relative to tumorigenesis strongly suggest that some of the alleles relevant to multispecific 'low' antibody production could contribute to the resistance to cutaneous chemical tumorigenesis.

Genetic regulation of macrophage functions.

Normal phagocytic function is genetically determined but maintained in a rather narrow range of variation. Phagocytosis stimulation induced by different agents is variable according to species, strains or individuals. Variation is environmental, to a great extent, but has also a genetic component which differs in each case. Selective breeding for macrophage responsiveness to triolein stimulation was successful. However, the relevant genes have only a small effect on antibody synthesis. Macrophages of mice selected for high and low antibody synthesis have a similar phagocytic function but their capacities of antigen processing are quite different.

[Plasmodium berghei: antibody response and protective immunity induced by vaccination]. / Plasmodium berghei: risposta anticorpale e immunità protettiva indotta da vaccinazioni.

The authors have studied the behaviour of Swiss mice and of 5 inbred strains of mice in order to investigate: the protective effect, in the homologous infection test, of six vaccine inoculations of irradiated parasites belonging to two strains of Plasmodium berghei: ISTISAN and K173; the capacity to produce humoral antibodies after vaccine treatments and during infection; the probable correlation between the high antibody titre and the protection against infection. The results of the present study show that the antibody response plays a precise role in the immunity induced by vaccination. There is a certain degree of correlation, which is more evident for K173 vaccine, between the level of antibody response during infection and the protective efficacy of vaccination.

In vitro immune response of spleen cells from mice genetically selected for high or low antibody production.

The aim of this study was the identification of the cell type in which genes selected for high or low response to SRBC express their functions. Spleen cells from high (H) and low (L) responder mice were immunized with SRBC in the Mishell and Dutton system. An antibody response of different magnitude was found in cultures of H and L spleen cells, the difference being at least as great as that observed in vivo. This finding under experimental conditions allowing the exclusion of any influence of the animal milieu during the immune response, suggest macrophages, B, and T lymphocytes as possible target cells of gene action. In vitro cell separation and recombination experiments in which spleen cells were immunized with SRBC, TNP-LPS, or TNP-HRBC indicate that the genetic differences between H and L responders brought about by selective breeding are expressed in lymphocytes to greater extent than in macrophages. The role of histoincompatibility in the recombination experiments in unlikely but cannot be excluded. Among lymphocytes, B cells but not helper T cells were found more responsive in cultures of spleen cells from H than from L mice.

IgA antibody response to intragastric immunization in high and low immune responder lines of mice.

Two lines of mice selected for genes controlling the character "quantitative agglutinin production" to heterologous erythrocytes were immunized orally by the intragastric administration of sheep red blood cells (SRBC). The quantity of circulating IgA anti-SRBC and the numbers of splenic plaque-forming cells of IgA and IgM classes were related to the genetic status of the animal lines.

Genetic selection for antibody responsiveness in mice: further evidence for inverse modification of macrophage catabolic activity without alteration of the expression of T-cell-mediated immunity.

Five selective breedings have been performed for the character "antibody production" in mice. Two of them, Selection I and Selection II, carried out for maximal (H) and minimal (L) antibody response to heterologous erythrocytes, gave similar results concerning the genetic parameters and the extent of modification of antibody response to unrelated antigens (non-specific effect of the selection). Macrophage characteristics and the expression of T-mediated immunity were investigated in H and L mice of Selection II and compared with results already obtained in Selection I. The phagocytic activity of macrophages was similar in the two lines, whereas an important interline difference was observed concerning the persistence of the immunogen, which was much shorter in L than in H mice. The more rapid antigen catabolism in L mice explains why the threshold immunogenic dose was higher in these mice and why the antibody response was much more improved in L than in H mice by repeated antigen administration. Results on skin allograft rejection, delayed-type hypersensitivity and responsiveness to T mitogen demonstrated that H and L mice have a similar ability to mount T-mediated immunity reactions. Two findings obtained in Selection I were therefore confirmed: 1) macrophage catabolic activity is modified by selection in the opposite direction of antibody production: low antibody responsiveness is associated with high macrophage activity and vice-versa; 2) and the expression of cell-mediated immunity and of the humoral immune response are at least partially under independent genetic regulation.