How much higher is the avidity of IgM compared to IgG assuming that both isotypes have the same affinity?
A)2-fold
B)5-fold
C)IgG had the same avidity as IgM
D)10-fold

The avidity of 1g M compared to 1g G assuming both isotopes have same affinity is ; ( B ) 5-fold.

The Avidity is the overall measure of strength of the connections between antibody and antigen and it is dependent on the affinity of the bond ( single ) between an antibody and antigen and the antigen binding sites.

Given that 1gM and 1gG both have the same affinity therefore to determine the ratio in the avidity of both isotypes is dependent on the number of antigen binding sites present in each isotype.

1gG = Bivalent ( 2 sites )

1gM = decavalent ( 10 sites )

∴ The avidity of 1gM compared to 1gG = 10 sites / 2 sites = 5 -folds .

Hence we can conclude that The avidity of 1g M compared to 1g G assuming both isotopes have same affinity is ; ( B ) 5-fold .

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