Which organ provides the site for interaction of lymphocytes with antigens?

State the number of polypeptide chains in $H_{2}L_{2}$ (an antibody molecule).

In an antibody,disulphide bonds are present . . . . . .
$i$. between two heavy chains
$ii$. between two light chains
$iii$. between the constant region of a light chain and the constant region of a heavy chain
$iv$. between antigen binding sites of both the heavy and light chains
$v$. between the variable region of a light chain and that of a heavy chain
Select the correct answer from the options given below.

In the case of a snakebite, the patient is injected with preformed antibodies against the snake venom. This type of immunity is called.........

Humans have an acquired immune system that produces antibodies to neutralize pathogens. Still,the innate immune system is present at the time of birth because it

Define Antigen and Antibody. Name any two diagnostic kits based upon them.