# Mechanism of Action
Keywords: TYSABRI, Mechanism of Action, MS, Multiple Sclerosis, PML, Blood-Brain Barrier, Antigen Presenting Cell, Central Nervous System

> This page provides information about TYSABRI's mechanism of action, its rapid onset and reversibility, and how it works to treat Multiple Sclerosis (MS). It also includes resources for healthcare professionals and patient support materials.

## Details
- [Mechanism of Action](#): Overview of TYSABRI's rapid onset of action and reversibility in treating MS.
- [How TYSABRI Works](#): A 4-minute video explaining the mechanism of action of TYSABRI.
- [Reversibility of TYSABRI](#): A 2-minute video detailing the reversibility of TYSABRI's effects.
- [Guard Dog Analogy](#): A 3-minute video using an analogy to explain MS and TYSABRI's mechanism of action.
- [Patient Support Materials](#): Downloadable TYSABRI IV and SC patient packs for healthcare professionals.
- [Adverse Event Reporting](#): Instructions for reporting adverse events in the UK and Ireland, including contact details.
- [References and Abbreviations](#): Definitions of technical terms and references to supporting studies.