1) This is the major serum Ig containing 75% of the total serum immunoglobulin concentration.

2) It has a molecular weight of 150,000 Daltons and sedimentation coefficient is seven.

3) Its half-life is approximately 23 days.

4) It is the Ig, which is normally transported across the placenta and provides natural passive immunity to the newborn

5) It participates in immunological reactions such as compliment fixation, precipitation, and neutralization of toxins and viruses.

6) It is secreted in large amounts during secondary immune response.