What is the full form of $HLA$?

Where are $B$-cells and $T$-cells formed? How do they differ from each other?

Which cells do not produce antibodies but help $B$-cells in the production of antibodies?

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 cells secrete interferons?

Which of the following is $NOT$ associated with lymphoid organs?