PROS1 and influenza: We fine-tuned the four antibody language models by training the last three layers of the pre-trained model along with sequence classification head to predict the specificity of SARS-CoV-2 S protein (Figure 2B, Table S3) and influenza HA (Figure 2D, Table S4) using the full-length paired BCR sequences and evaluated the performance of fine-tuning on the test set by the same data split using the four-fold cross validation procedure as the pre-trained embedding procedure.