An antibody is a

Plasma cells are .....

Many microbial pathogens enter the gut of humans along with food. What are the preventive barriers to protect the body from such pathogens? What type of immunity do you observe in this case?

Identify the correct statements from the following:
$(i)$ The skin is the main physical barrier.
$(ii)$ Mucus coating of the epithelium lining the respiratory,gastrointestinal,and urogenital tracts is a physiological barrier.
$(iii)$ $IgA, IgM, IgE, IgG$ are types of $T$-cells.
$(iv)$ The primary immune response is very intense.

Which of the following organs are primary lymphoid organs?

Which of the following is the function of $T-$cells?