A developing foetus receives some antibodies from the mother through the placenta during pregnancy. After birth, the newborn infant receives antibodies from the mother through colostrum. Identify the primary antibody types involved in the first and second cases respectively, and the specific type of immunity they represent.

Step-by-step solution

The foetus receives IgG antibodies from the mother through the placenta, which is the only antibody class capable of crossing the placental barrier. After birth, the infant receives IgA antibodies, which are abundantly present in colostrum (the yellowish fluid secreted during the initial days of lactation). In both cases, pre-formed antibodies are directly transferred from the mother to the child to provide immediate protection. This transfer of ready-made antibodies under natural physiological conditions is an exa