TABLE 5-2 COMBINATORIAL ANTIBODY DIVERSITY IN HUMANS AND MICE Light chains Multiple germ-line segments Heavy chain Estimated number of segments in humans* 51 40 30 D 27 0 0 6 Combinatorial V-D-J and V-]joining 51×27×6=8262 40×5=200 30×4=120 (possible number of combinations) Possible combinatorial associations of heavy and light chains 8262×(200+120)=2.64×10 Estimated number of segments in mice' 134 85 D 13 0 0 4 4 3 Combinatorial V-D-J and V-I joining 134×13×4=6968 85×4=340 2×3=6 (possible number of combinations) Possible combinatorial associations of heavy and light chains' 6968×(340+6)=2.41×10 These numbers have been determined from studies of single.slight differences may be seen among ditterent individuals.Also,in the human case,only the functional gene segments have been listed.The genome contains additional segments that are incapable of rearrangement or contain stop codons or both. In the mouse case.the figures contained in the table are only best estimates,because the locus has not been completely sequenced. Becaus of the iversity coributed by junctional flexibility.P.region nudetide addition.N-region nucete addition,and somatic mutation,the actual potential excceds these estimates by sveral orders of magnitude