Amazon, Apple, Ebay and 50 other companies have joined an amcius brief in support of transgender student Gavin Grimm, the teen at the center of the bathroom access debate.

Grimm is the Gloucester High School senior who is challenging his school district's policy that prohibits transgender students such as himself from using the bathroom of their choice. The Supreme Court is expected to hear arguments in the case on March 28.

(Related: Laverne Cox on The View calls transgender teen Gavin Grimm “inspiring.”)

“These companies are sending a powerful message to transgender children and their families that America’s leading businesses have their backs,” said Chad Griffin, president of the Human Rights Campaign (HRC), the nation's largest LGBT rights advocate. “Across the country, corporate leaders are speaking out because they know attacking transgender youth isn't just shameful – it also puts the families of their employees and customers at risk. Transgender students like Gavin are entitled to the full protection of the law, and must be affirmed, respected and protected in the classroom and beyond.”

The 53 companies that signed the brief represent over 1.3 million employees and $613 billion in revenue, according to an HRC statement.

Companies that signed on to the brief include Affirm, Inc., Airbnb, Inc.,, Inc., Apple, Asana, Inc., Box, Inc., Codecademy, Credo Mobile, Inc., Dropbox, Inc., eBay Inc., Etsy, Fastly, Inc., Flipboard, Inc., Gap Inc., General Assembly, GitHub, Inc., IBM, Intel Corporation, Kickstarter, PBC, Knotel, Inc., LinkedIn, Lyft, M Booth, MAC Cosmetics Inc., Mapbox, Inc., Marin Software Incorporated, Massachusetts Mutual Life Insurance, Microsoft Corporation, Mitchell Gold + Bob Williams, MongoDB Inc., NetApp, Inc., Next Fifteen Communications Corporation, Nextdoor, Pandora Media, Inc., PayPal Holdings, Inc., Postmates Inc., Replacements, Ltd., RetailMeNot, Inc., Salesforce, Shutterstock, Inc., Slack Technologies, Inc., Spotify, The OutCast Agency, The WhiteWave Foods Company, Tumblr, Inc., Twilio Inc., Twitter Inc., Udacity, Inc., Warby Parker, Williams-Sonoma, Inc., Yahoo! Inc., Yelp Inc., and Zendesk, Inc.