X0306 4 2022-06-28 0 0001532346 Atreca, Inc. BCEL 0001278410 Serafini Tito C/O ATRECA, INC., 835 INDUSTRIAL RD. SUITE 400 SAN CARLOS CA 94070 1 1 0 0 Chief Strategy Officer Class A Common Stock 50000 I By the Serafini/Postner Irrevocable Remainder Trust Class A Common Stock 2022-06-28 4 S 0 15000 2.0177 D 228875 I By the Serafini/Postner Revocable Trust Class A Common Stock 42200 D The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan. The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $2.00 to $2.04, inclusive. The Reporting Person undertakes to provide to Issuer, any security holder of Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this Form 4. /s/ Courtney Phillips, attorney-in-fact 2022-06-30