Wow, learn something new everyday!! Yes you have it right T cells are the in storage cells; in mammals the IgG is the cells in the colostrum that is abosorbed thru the intestines. I wonder which can do this , or if it applies to all. THanks for the update.Actually, the hens DO pass immunities through the eggs. When reading up on vaccinations, if a flock is vaccinated for some things, then the day old chicks shouldn't be vaccinated until after, I believe, 6-8 weeks, because their mother's passive, natural immunities will kill off the vaccine strain before the chick's actual immunity (T cells?! memory is fading already, lol) can "get ahold" of the virus and start recreating those immunity cells. The natural passive immunities wear off in about 6-8 weeks and no longer protect them.