A critical role for lymphotoxin in experimental allergic encephalomyelitis

Abstract

The lymphotoxin (LT)/tumor necrosis factor (TNF) family has been implicated in the neurologic inflammatory diseases multiple sclerosis (MS) and experimental allergic encephalomyelitis (EAE). To determine the role of individual family members in EAE, C57BL/6 mice, LT-alpha-deficient (LT-alpha-/- mice), or LT-beta-deficient (LT-beta-/- mice), and their wild-type (WT) littermates were immunized with rat myelin oligodendrocyte glycoprotein (MOG) peptide 35-55. C57BL/6 and WT mice developed chronic, sustained paralytic disease with average maximum clinical scores of 3.5 and disease indices (a measure of day of onset and sustained disease scores) ranging from 367 to 663 with central nervous system (CNS) inflammation and demyelination. LT-alpha-/- mice were primed so that their splenic lymphocytes proliferated in response to MOG 35-55 and the mice produced anti-MOG antibody. However, LT-alpha-/- mice were quite resistant to EAE with low average clinical scores (<1), an average disease index of 61, and the negligible CNS inflammation and demyelination. WT T cells transferred EAE to LT-alpha-/- recipients. LT-beta-/- mice were susceptible to EAE, though less than WT, with an average maximum clinical score of 1.9 and disease index of 312. These data implicate T cell production of LT-alpha in MOG EAE and support a major role for LT-alpha3, a minor role for the LT-alpha/beta complex, and by inference, no role for TNF-alpha.

Figure 1

C57BL/6 mice develop a sustained chronic disease after immunization with MOG 35–55. Mice were injected with MOG peptide 35–55 in CFA and Pt as indicated in Materials and Methods. Mice that died are indicated and their scores are not included further in the graph.

Figure 2

LT-α^−/− mice manifest minimal clinical signs of EAE after active immunization. The average clinical signs of mice in the individual groups of C57BL/6 (▪), LT-α^+/− (•), and LT-α^−/− (○) mice are indicated. The scores of the 2 out of 6 C57BL/6 mice that died are included in the graph throughout the experiment. No other mice died.

Figure 3

LT-α^−/− show minimal CNS inflammation and demyelination after active immunization with MOG peptide. (A and B) Paraffin sections of spinal cord at day 30 of C57BL/6 (score 2.5) and (C) LT-α^−/− (score 0.5) mice stained with hematoxylin and eosin (A and C) and Luxol fast blue with neutral red (B). Note extensive infiltration of mononuclear cells and demyelination in sections of the control mice and minimal infiltration and no demyelination in sections from LT-α^−/− mice. (Original magnification of A–C × 125). (D) Epon toluidine blue section of infiltrating mononuclear cells in spinal cord of C57BL/6 mouse 35 d after immunization with MOG (Original magnification: × 312.5). Some demyelination is apparent.