Efficient peripheral clonal elimination of B lymphocytes in MRL/lpr mice bearing autoantibody transgenes

Abstract

Peripheral B cell tolerance was studied in mice of the autoimmune-prone, Fas-deficient MRL/ lpr.H-2(d) genetic background by introducing a transgene that directs expression of membrane-bound H-2Kb antigen to liver and kidney (MT-Kb) and a second transgene encoding antibody reactive with this antigen (3-83mu delta, anti-Kk,b). Control immunoglobulin transgenic (Ig-Tg) MRL/lpr.H-2(d) mice lacking the Kb antigen had large numbers of splenic and lymph node B cells bearing the transgene-encoded specificity, whereas B cells of the double transgenic (Dbl-Tg) MRL/lpr.H-2(d) mice were deleted as efficiently as in Dbl-Tg mice of a nonautoimmune B10.D2 genetic background. In spite of the severely restricted peripheral B cell repertoire of the Ig-Tg MRL/lpr.H-2(d) mice, and notwithstanding deletion of the autospecific B cell population in the Dbl-Tg MRL/lpr.H-2(d) mice, both types of mice developed lymphoproliferation and exhibited elevated levels of IgG anti-chromatin autoantibodies. Interestingly, Dbl-Tg MRL/lpr.H-2(d) mice had a shorter lifespan than Ig-Tg MRL/lpr.H-2(d) mice, apparently as an indirect result of their relative B cell lymphopenia. These data suggest that in MRL/lpr mice peripheral B cell tolerance is not globally defective, but that certain B cells with receptors specific for nuclear antigens are regulated differently than are cells reactive to membrane autoantigens.

Figure 6

Effect of transgenes on autoimmune disease in MRL/lpr.H-2^d mice. (A) Effect of transgenes and the MRL/lpr genetic background on lymph node hyperplasia. Data represent the means ± SE of three (young mice) and five (aged mice) experiments. (B) Survival of the various mouse strains. Inset shows number of mice/group.

Figure 1

Absence of 3-83 idiotype⁺ B cells in the lymph nodes of young Dbl-Tg MRL/lpr.H-2^d mice. (A–G) Flow cytometric analysis of lymph nodes of young (6–8 wk) mice of the indicated genetic backgrounds stained to reveal IgM⁺ and idiotype⁺ cells. (H) Summary of the effect of the autoimmune background on the percentage of idiotype⁺ B cells in lymph nodes. D shows representative data from a Dbl-Tg MRL/lpr.H-2^d mouse. C shows representative lymph node cells taken from a Dbl-Tg MRL/lpr/+.H-2^d Fas-sufficient control. Data represents the means ± SE of three independent experiments.

Figure 2

Absence of 3-83 idiotype⁺ B cells in the lymph nodes of Ig-Tg→ MT-K^b bone marrow chimeric mice. Flow cytometric analysis of B cells isolated from the lymph nodes of chimeric mice. Lymph node cells were stained to reveal IgM⁺ and idiotype⁺ B cells.

Figure 3

Efficient deletion of 3-83 idiotype⁺ B cells in the lymph nodes of aged Dbl-Tg MRL/lpr.H-2^d mice. (A–F) Flow cytometric analysis of lymph node cells of 5–7-mo-old mice of the indicated genetic backgrounds. Also shown are lymph node cells of age-matched B10.D2 controls. (G) Summarized data represents the means ± SE of five independent experiments.

Figure 4

Ig-Tg MRL/lpr.H-2^d mice produce comparable numbers of idiotype⁺ B cells compared with B10.D2 controls. Absolute numbers of idiotype⁺ B cells in the lymph nodes was calculated as (total cells) × (% idiotype⁺) as determined by FACS^® analyses. Total cells represents pooled cells from the inguinal, brachial, axillary and mesenteric lymph nodes of each mouse tested. Data represents the means ± SE of three (young mice) and five (aged mice) independent experiments.

Figure 5

Effect of genetic background and transgenes on development of IgG anti-chromatin autoantibodies. Serum antibody was quantified by ELISA.