Figure 7.2
A: The pre-B-cell receptor (pre-BCR). B: The B-cell receptor (BCR). The heavy chain of the pre-BCR is a m chain; the heavy chain of the BCR may be a m, d, g, a, or e chain. The immunoreceptor tyrosine-based activation motif (ITAM, discussed later in this chapter) is depicted as a rectangle in the Iga and Igb polypeptides.