Alteration in lymphocyte recognition repertoire during aging. II. Changes in the expressed T-cell receptor repertoire in aged mice and the persistence of that change after transplantation to a new differentiative environment

Changes in integrin/adhesion molecule expression, but not in the T-cell receptor repertoire, in old mice infected with tuberculosis

The results of this study present data in support of the hypothesis that T lymphocytes in both young and old mice infected with virulent Mycobacterium tuberculosis undergo changes in expression of cell surface integrin/adhesion molecules as determined by flow cytometric analysis. These data thus further support the hypothesis that a reduced ability of T-cells in old mice to adequately and promptly accumulate at sites of inflammation induced by bacterial implantation is a central parameter underlying the increased susceptibility of these mice to this intracellular bacterial infection. In addition, however, no changes were observed in terms of the T-cell receptor expression (repertoire) of these animals, indicating that this facet of immunity is preserved in aging.

Age-related changes within a suppressor T cell circuit

The effects of aging on cellular and molecular components of the 4-hydroxy-3-nitrophenyl acetyl-specific suppressor T (Ts) cell circuit were analyzed in vitro using inducer (Ts1), transducer (Ts2), and effector (Ts3) cells and activating factors (TsF1 and TsF2) derived from young or old mice. The activation of Ts2 cells by TsF1 and of Ts3 cells by TsF2 was found age-restricted, suggesting a loss of Ts2 and Ts3 cell subsets in old mice. However, the activation of Ts3 cells by small amounts of TsF2 is more efficient when both are derived from old rather than from young mice while the same level of maximum suppression is attained. Higher affinity of the interactions involved in Ts cell activation may compensate for loss of Ts cell subsets in old mice. No age restriction was found for antigen presentation to Ts1 cells and for the interaction between Ts3 cells and target B cells. Thus, the effects of aging on immunosuppression result from changes within the Ts cell circuit.

Age-related changes in the degeneracy of the mouse T-cell repertoire

Aging is associated with a decline in T-cell-dependent immune responses. As the number of T-cells remains relatively constant throughout life, the observed decline in T-cell function may reflect qualitative changes in the T-cells themselves or in the composition of the T-cell population. In this investigation, the quality of the T-cell response was studied in young-adult and aged B6C3F1 mice by assessing the degeneracy of the hapten-specific proliferative response to the antigen-MHC complex. Degeneracy was defined as the ability of lymph node cells from mice contact-sensitized to the hapten TNP to proliferate in response to in vitro stimulation with haptenated allogeneic antigen-presenting cells, thus escaping strict MHC restriction. It was found that, although degeneracy occurred in both age groups, it was more prevalent and of a greater magnitude in the young than in the old lymphocytes. These results suggest that there are qualitative differences in T-cell populations derived from young-adult and aged mice.

Alterations in the human immune response to the hepatitis B vaccine among the elderly

The specific binding of hepatitis B (HBs) antigen by lymphocytes from old people immunized with hepatitis B vaccine was explored. For that purpose HBs antigen was combined with fluorescent microspheres, and labeled antigen was allowed to react with lymphocytes from HBs vaccine-responsive or unresponsive people. Lymphocytes from 10 responders and 14 nonresponders were tested for their antigen-binding ability. For controls, lymphocytes were incubated with microspheres bearing human albumin. Lymphocytes from 8 out of 10 responders were able to recognize HBs antigen; for the nonresponders the ratio was 9 out of 14. HBs-binding lymphocytes were B cells but not T lymphocytes. B and T cells from responders and nonresponders were combined and cultivated for 8 days in the presence of HBs antigen, and antibody-producing cells were counted. Neither B cells alone nor B cells plus T cells from nonresponders were able to produce antibody. On the other hand B cells from unresponsive old people produced antibodies when they were cultivated in the presence of HBs antigen and T cells from responsive old people. These data suggest that some elderly individuals who do not produce antibody after in vivo immunization by HBs vaccine do have antibody-producing cells. Instead of a gap in their immune repertoire, these people are suffering from immune dysfunction.

Deterioration of cellular immunity during aging. The relationship between age-dependent impairment of delayed-type hypersensitivity reactivity, interleukin-2 production capacity, and frequency of Thy-1+,Lyt-2- cells in C57BL/Ka and CBA/Rij mice

The effect of aging on the delayed-type hypersensitivity (DTH) to sheep red blood cells (SRBC) in vivo and the interleukin-2 (IL-2) production capacity in vitro by spleen cells from young (17 weeks) and old (125 weeks) CBA/Rij and C57BL/Ka mice were investigated. For both CBA/Rij and C57BL/Ka mice an age-related decline in the DTH response to SRBC and the IL-2 production capacity was observed. Both parameters are mediated by Thy-1+,Lyt-2- spleen cells. For both mouse strains the proportion of Thy-1+,Lyt-2- spleen cells declined less strongly with aging than the DTH reactivity and the IL-2 production capacity. From this it was concluded that not only a quantitative but also a qualitative decrease of T-cell function occurs during senescence. It was also investigated whether the proportion of Thy-1+,Lyt-2- peripheral blood lymphocytes can be used as a predictive value with regard to the decline of DTH with aging of the corresponding mouse. This was indeed found to be the case in CBA/Rij mice, but not in C57BL mice.

Respective roles of immune and nutritional factors in the priming of the immune response in the elderly

Ninety-six institutionalized elderly (greater than 70 years old) (mean age: 82 +/- 7 years) subjects, negative for tetanus toxoid antibodies were primed with tetanus toxoid vaccination and dinitrochlorobenzene (DNCB). Correlations were studied between some immunological parameters, nutritional parameters prior to immunization and the immune response intensity after it. Levels of tetanus toxoid specific IgG (ELISA assay) were positively correlated with monocyte phagocytosis, DNCB response and prealbumin levels, and negatively correlated with total IgG, monocyte immune degradation and tetanus toxoid lymphocyte stimulation. No correlation was observed with IgA, IgM, PHA stimulation. Tetanus toxoid lymphocyte stimulation correlated positively with response to DNCB, and negatively with tetanus toxoid IgG as well as total IgG. DNCB response correlated with prealbumin, tetanus toxoid IgG and tetanus toxoid lymphocyte stimulation. Therefore, it appears that malnutrition, as measured by prealbumin level, is one of the main factors contributing to the inconstant senile immunodeficiency. Monocyte antigenic degradation function unaltered with age can impair immune response while conserved or increased phagocytosis enhances immune response in the elderly. High total IgG levels were linked with low specific responses to priming antigens. High specific antibody levels also correlated negatively with cellular specific response. It is assumed that regulatory IgG antibody accumulation, likely anti-idiotypic antibodies, play an important role in senile immunological depletion.

Alterations in lymphocyte recognition repertoire during ageing. I. Analysis of changes in immune response potential of B lymphocytes from non-immunized aged mice, and the role of accessory cells in the expression of that potential

The repertoire of specificities recognized by endogenous plaque-forming cells of young or aged mice has been examined, as well as the repertoire of specificities represented by mitogen-activated B cells of those animals. Significant changes occur in both polyclonal endogenous plaque-forming cells and polyclonal B cell responsiveness, as well as reactivity for antigens expressed on bromelain-treated mouse erythrocytes and mouse Ig-coupled sheep erythrocytes. Adoptive transfer experiments suggest that these changes reflect a role for the differentiative environment in the regulation of the B cell recognition repertoire. Additional analysis of changes in antigen-presenting cells in aged mice suggest that alterations in the manner of presentation of environmental antigens in vivo may control the expressed B cell repertoire. Indeed, under experimental conditions it has proven less easy to induce B cell/macrophage restriction (for antigen presentation and induction of antibody formation) in cells of old animals than in cells of younger mice.