Yolande Bouthillier

A Major Role of the Macrophage in Quantitative Genetic Regulation of Immunoresponsiveness and Antiinfectious Immunity

Publisher Summary It is clear today that the immune system is constituted by a coordinated network of perfectly integrated and interacting cells and molecules subject to strict cooperation to ensure the highest possible efficiency in antiinfectious immunity. A simplified scheme of the immune system in higher vertebrates is represented in this chapter. The enzyme equipment of macrophage phagosomes endows these cells with bactericidal or bacteriostatic activity on ingested microorganisms, therefore, constituting the first important mechanism in antiinfectious defense. The metabolic activity of macrophages on engulfed antigens also regulates the specific response of T and B lymphocytes through a complex process of antigen handling and antigen presentation, establishing a sort of symbiotic relationship between lymphocytes and macrophages. There are two essential components in the immune response: one is specific and the other nonspecific. The specific response involves the stereospecific selective recognition. The nonspecific aspect of the immune response includes the handling of the phagocytized antigen and the rate at which the process of multiplication and differentiation of small lymphocytes takes place. The protective effect of specific vaccination is essentially based on immunological memory. The antibody molecules, according to their isotypes, play specialized defensive roles against various types of invading microorganisms, particularly in collaboration with the complement system, inducing bactericidal or opsonizing effects.

Basal immunoglobulin serum concentration and isotype distribution in relation to the polygenic control of antibody responsiveness in mice

Serum Ig concentration and isotype distribution were determined in the high (H) and low (L) responder lines selected for antibody response to complex immunogens. Data were recorded in normal and postimmunization sera from the H and L lines produced by five independent selective breedings (selections I, 11, III, IV, and V). Ig levels were much higher in H than in L mice of all the selections. In four selections this interline difference increased further after immunization with the selection antigens. This is in agreement with the general effect of the polygenic control of antibody responses operating in H and L lines. The Ig isotype profiles of normal sera were different in each line; however, similitudes were noticed between H and L lines in selections I and If. In contrast, in selections III, IV, and V a similar interline difference was observed: the lack of IgG2a isotype in L lines only. After immunization there were minor alterations of the isotype profiles except in the H lines of selections III and IV, in which a clear inverse modification of IgG1 and IgG2a proportions occurred. The characteristic pattern of each selection may be partially dependent on isotype-restricted regulatory effects in relation to the immunization procedure used for selective breeding.

Interaction ofH-2 and nonH-2 linked genes in the regulation of antibody response to a threshold dose of sheep erythrocytes

The antibody response to a threshold dose (10) of SE was studied in the High responder line (H) and the Low responder line (L) of mice obtained by bidirectional selective breeding for the character “quantitative agglutinin response” to an optimal dose of SE, and in interline hybrids: F1, F1 and both backcrosses. Whereas the interline difference in agglutinin responses at the optimal dose is due to the additive effect of about ten independently segregating loci, one of which isH-2 linked, the responsiveness to the threshold dose is determined by the effect of two loci. The direction of the dominance effect also varies with the antigen dose: high responsiveness is partially dominant at the optimal dose while at the threshold dose nonresponder character is partially dominant. The role of theH-2 linked locus was investigated. It has been demonstrated that on an identical background (equivalent to that of F1 hybrids) this locus is responsible for 12% of the interline difference at the optimal antigen dose, and for 61% at the threshold antigen dose. For the two antigen doses, the quantitative effect of theH-2 locus is in agreement with the estimate of the number of loci obtained by variance analysis. The intervention of a second gene, non-H-2 linked, in the regulation of responsiveness to 106 SE is demonstrated by appropriate assortative matings. The interaction between the two genes is discussed.

Skin tumorigenesis by initiators and promoters of different chemical structures in lines of mice selectively bred for resistance (Car-r) or susceptibility (Car-s) to two-stage skin carcinogenesis.

Carcinogenesis‐resistant (Car‐R) and carcinogenesis‐susceptible (Car‐S) mice were obtained applying a bi‐directional selective breeding approach to a two‐stage skin carcinogenesis protocol, using 9,10‐dimethyl‐1,2‐benzanthracene (DMBA) as initiator and 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA) as promoter. Sixteen generations of selection produced a remarkable interline difference in responsiveness to two‐stage skin carcinogenesis between Car‐R and Car‐S: identical DMBA (25 μg) and TPA (5 μg) doses induced papillomas in 100% of Car‐S compared with 3.3% of Car‐R mice and maximal responses of 14.3 or 0.03 papillomas/mouse, respectively, despite the shorter promotion applied to Car‐S (49 vs. 208 days). To define the factors determining this great difference, Car‐R and Car‐S mice were challenged by initiators/promoters chemically unrelated to those used for selection. Both lines were subjected to either initiation by N‐methyl‐N‐nitrosourea (MNU) followed by TPA promotion, or promotion by benzoyl peroxide, or 1,8‐dihydroxy‐3‐methyl‐9‐anthrone (chrysarobin) following DMBA initiation. Initiation with MNU induced a 10‐fold tumour incidence in Car‐S compared with Car‐R mice, and a 32‐fold difference in tumour induction rate. The 2 lines also differed markedly in susceptibility to benzoyl peroxide promotion: Car‐S mice initiated with 25 μg DMBA and promoted with 7.5 mg benzoyl peroxide showed a 12‐fold tumour incidence and a 103‐fold tumour induction rate compared with the corresponding Car‐R group. Both lines, however, were refractory to chrysarobin promotion. The progression of papillomas to carcinomas was examined in all Car‐S groups. The incidence of mice that developed carcinomas was 57% in MNU‐initiated mice. Benzoyl peroxide was also able to promote carcinoma development in Car‐S mice, though with a lower incidence (30.4%) than TPA. Int. J. Cancer 83:335–340, 1999.

Polymorphism of Tcrb and Tcrg genes in Biozzi mice : segregation analysis of a new Tcrg haplotype with antibody responsiveness

Tcrb andTcrg gene polymorphism was investigated in high (H) and low (L) responder Biozzi mice from selection I, II, and GS by Southern blot analysis with appropriateV andC probes. No polymorphism of theTcrb haplotype was detected between H and L mice in all selections which were all found to be of the BALB/c type. The H-I and H-II g genotype was of BALB/c and DBA/2 type, respectively. In contrast, a newTcrg haplotype shared by L-I and L-II mice was identified and characterized by Cγ1, 2, 3, Cγ4, Vγ1, 2, 3, Vγ5, and Vγ6 restriction fragment length polymorphisms (RFLPs).Tcrg genotypes were not fixed in the GS selection and two additional new haplotypes were identified in two L-GS mice. An attempt was made to correlate the L-Ig genotype with the low responder status by analyzingg haplotypes among highest and lowest responder (H-1 x L-I)F2 hybrids immunized with sheep red blood cells (SRBC). No correlation was found in this segregation study, whereas a highly significant one was established with theH-2 haplotype, a locus already known to participate in the genetic control of H-I/L-I difference. The lack of correlation between SRBC response and theTcrg genotype was consistent with the heterogenousg haplotypes found in mice of the GS selection. Together, the present results suggest that H and L mice have the sameTcrab potential repertoire and that T-cell receptor (Tcr) genes cannot be considered as immune response genes in this model. Our results also indicate that the F2 segregation analysis, given a polymorphic gene, is suitable for an investigation of its immune response functions.

INTERACTIONS BETWEEN H-2 AND BACKGROUND GENES MODULATE COLLAGEN INDUCED ARTHRITIS IN HIGH (HI) AND LOW (LI) ANTIBODY PRODUCER BIOZZI MICE

The experimental arthritis (collagen induced arthritis, CIA) induced in mice by heterologous collagen of type II is mainly restricted to the H-2q or H-2r haplotypes. However, data including ours, strongly suggest that CIA is also under non MHC polygenic control. This point has been studied in new sub-strains of high (HI) and low (LI) Biozzi mice made congenic for H-2q and H-2s: the original Biozzi lines HI/H-2q and LI/H-2s and the new HI/H-2s, LI/H-2q congenic mice. 80% of the HI/H-2q mice develop severe chronic inflammatory symptoms with joint deformation and swelling soon after induction of the disease, while 60% of LI/H-2q counterpart develop at a later stage, deformation of joints with no or mild swelling. In the H-2s haplotype, considered to be non or weakly permissive to CIA, 40% of HI/H-2s have strong CIA symptoms; the LI/H-2s being totally refractory. Thus, if MHC products play a crucial role in selecting the arthritogenic epitope of CII; non H-2 genes strongly modulate the severity of experimental arthritis.