A cell population study of IgM affinity maturation

Affinity and distribution of subpopulations of antibody-producing cells in protein-restricted C57BL/6 mice

To study the effect of protein restriction on the affinity of antibodies produced by plaque-forming cells (PFC), C57BL/6 mice were fed diets containing 4% (R4%), 8% (R8%), or 27% (N) casein for 2 (short-term) or 12 (long-term) weeks and immunized with dinitrophenyl (DNP) bovine gamma-globulin in complete Freund's adjuvant. Affinity was assessed by inhibition of plaque formation in the presence of free hapten. Anti-DNP PFC per 10(7) spleen cells were not diminished in short- and long-term R8% mice, and were increased in the former group at certain times after immunization. Affinity of indirect PFC was increased at Days 14 and 21 after immunization in short-term R8% mice and at Day 7 in R4% mice, and was similar in long-term R8% and N animals. No limitation in the heterogeneity of PFC affinities was observed in the restricted groups. Short-term restricted mice showed a rise of the high-affinity PFC subpopulation. The number of mice with hapten-augmentable PFC was diminished in the short-term R8% group at 7 days after immunization and in long-term restricted mice at 14 days, suggesting depressed levels of auto-anti-idiotypic antibodies in protein restriction.

Allotype and charge-related differences in the immune response

Rabbits homozygous at the Ab kappa chain allotypic locus (Ab4/Ab4 and Ab9/Ab9) were immunized with negatively and positively charged antigens. The negatively charged antigens were bovine serum serum albumin (BSA; pI = 4.9), ovalbumin (OV; pI = 4.9) and two synthetic polypeptides: copolymer L-glutamic acid L-tyrosine (abbreviated TG; pI = 4.8) and multichain poly (L-tyrosine: L-glutamic acid) poly D-alanine: poly L-lysine (poly L-lysine backbone) abbreviated (TG) --AL; pI = 4.8). The positively charged antigen was hen egg lysozyme (LYS; pI = 10.2). Homozygous Ab9 rabbits responding to negatively charged antigens made less antibody than did Ab4 homozygotes. In contrast, both groups of animals responded equally well to positively charged lysozyme. The relative electric charges of the antibodies were assessed by Sephadex A-50 chromatography. The charge distribution was found to depend on the charge of the eliciting antigen. The positively charged antibodies of Ab9/Ab9 rabbits were not nearly as positively charged as those raised in Ab4/Ab4 rabbits. The difference in average electric charges and in the range of these charges between Ig Ab4 and Ig Ab9 explain quantitative differences in antibody formation in response to negatively charged antigens and may be a contributing factor to the "pecking order", i.e. unequal phenotypic expression of light chain genes in Ab4/Ab9 heterozygotes.

Analysis of antibody populations to oligo-D-alanine. VIII. Sequential studies on properties of antibody subpopulations: rate constant, affinity, and isoelectric focusing spectrum

Allotypically marked antisera to the hapten oligo-D-alanine were studied over periods up to 10 months in individual mice and in serial transfers of both nonimmune and memory cells to irradiated recipients. Parameters observed were divalent association rate constants, affinity and autoradiography of isoelectric focusing (IEF) spectra. The two allotypic subpopulations of heterozygous mice are shown to be independent with respect to affinity. Association rate constant, affinity, and IEF spectra of the antibody populations remain largely stable in most mice over prolonged periods. There is an occasional isolated dramatic change in a single property of one allotypic subpopulation; this may be in the direction of either lower or higher rate constant or affinity. While different recipients of naive spleen cells from a single donor, when immunized, differ one from the other in the measured antibody properties, the characteristics now established in each recipient persist in a lineage of transferred memory cells up to 4 generations, with infrequent changes in isolated properties of only one allotypic subpopulation. The limited changes observed would be in agreement with a model of moderate somatic variability superimposed on a small spectrum of germ line genes.

The role of B-cell memory in secondary IgG and IgM responses

Mice were primed with the hapten 3-nitro-4-hydroxy-5 iodophenacetic acid (NIP) conjugated to chicken globulin (cg) and were boosted 2, 6, or 12 months later with CG conjugates of the related haptens 3,5-diiodo-4-hydroxyphenacetic acid (DIP) or 3-nitro-4-hydroxphenacetic acid (NP). Accelerated secondary responses were demonstrated both in the 7S and 19S class. Fine-specificities of secondary-response antibodies were studied by the hapten inhibition method of haptenated bacteriophage inactivation. 7S antibodies were found to have the fine-specificity of anti-NIP antibodies regardless of whether DIP or NP was the booster hapten ('original antigenic sin'). 19S antibodies had the fine-specificity of anti-DIP when DIP was the booster hapten. NP as the booster hapten resulted in 19S antibodies whose fine-specificity was intermediate between anti-NIP and anti-NP. A strong B-cell memory could thus be demonstrated in the 7S antibody response and a weak B-cell memory in the 19S antibody response.

Lymphocyte proliferation in vitro induced by hapten autologous protein conjugates. I. A study on the class of lymphocytes responding in vitro and on the nature and specificity of their receptors

Immune lymph node cells from guinea pigs respond to soluble antigen in vitro by an increase in DNA synthesis. Optimal conditions for this proliferative response were studied in the present article. Under such conditions, immune cells showed increasing responses with increasing antigen concentration in vitro, the threshold dose of activation frequently being as low as 0.02 microg per culture. In contrast, normal lymph node cells (from FCA-stimulated animals) did only respond to antigen at very high doses (20 mg/culture), and immune cell dilution studies could be performed in normal cells without changing the kinetics of the antigen specific response of immune cells. Fractionation on anti-Ig columns indicated that purified, immune T lymphocytes were quite capable of proliferating in vitro upon antigen stimulation. However, our attempts to adsorb the proliferating cells onto chemically defined immunoadsorbants failed despite the fact that immune B cells (as measured by the rosette assay) were retained almost completely by such a procedure. Purified, immune T lymphocytes from guinea pigs immunized with different antigen concentrations in vivo and/or obtained at different times after immunization were tested for a differential sensitivity toward antigen-induced DNA synthesis in vitro. However, we were not able to demonstrate any regular increase in sensitivity to antigen in vitro, and if found, it seemed to be more dependent upon the number of antigen reactive cells in the population studied rather than upon differences in the average avidity of the receptors on the cells proliferating in vitro. The results in the present article are discussed in relation to current knowledge and hypotheses on T-lymphocyte receptors.