Rallies in the shares of the biggest technology company's helped lift the tech-heavy Nasdaq 100 /zigman2/quotes/210598364/realtime NDX -1.95% to a healthy gain, even as the broader stock market was selling off. The Nasdaq 100 climbed 1.3% in afternoon trading, reversing an earlier drop of as much as 1.9%, as the index's top-five most valuable companies by market capitalization all rose. Shares of Apple Inc. /zigman2/quotes/202934861/composite AAPL -1.51% gained 1.5%, Microsoft Corp. /zigman2/quotes/207732364/composite MSFT -1.39% rose 1.0%, Alphabet Inc. /zigman2/quotes/202490156/composite GOOGL -2.46% /zigman2/quotes/205453964/composite GOOG -2.27% ran up 3.8%, Amazon.com Inc. /zigman2/quotes/210331248/composite AMZN -2.86% advanced 3.6% and Tesla Inc. /zigman2/quotes/203558040/composite TSLA -2.05% tacked on 1.9%. The index's biggest gainer was early-pandemic beneficiary Zoom Video Communications Inc.'s stock /zigman2/quotes/211319643/composite ZM -3.57% , which rose 7.8%. Meanwhile, the Dow Jones Industrial Average /zigman2/quotes/210598065/realtime DJIA -0.86% slumped 279 points, or 0.9%, and the S&P 500 /zigman2/quotes/210599714/realtime SPX -1.29% declined 0.9%.