Final answer:
Conjugate vaccines utilize the hapten-carrier concept to enhance the immune response by attaching polysaccharide antigens to carrier proteins, creating a more effective antigen that can stimulate both B and T lymphocyte activity, making them particularly valuable for young children who can't respond well to polysaccharides alone.
Step-by-step explanation:
The principle of conjugate vaccines is based on the hapten-carrier concept, where small molecules called haptens are attached to larger carrier proteins to form a more effective antigen. These haptens, when conjugated to carrier proteins, can then elicit a stronger and more effective immune response in the body. Conjugate vaccines are particularly important for young children, who do not mount a strong immune response to polysaccharide antigens on their own. By using a carrier protein with T-dependent antigens, the production of antibodies against both the protein and the capsule polysaccharide is stimulated. This is crucial for combating infections by pathogens surrounded by protective polysaccharide capsules, which can evade the immune system and cause diseases such as meningitis.
Conjugated proteins carry non-peptidic portions, which, when attached to haptens, create the conjugate antigen needed to stimulate the immune response. These conjugate vaccines are essential in some cases because children under two years of age generally do not have a robust response to T-independent capsular polysaccharide antigens. The conjugation with a protein renders the antigen T-dependent, facilitating a better immune response involving both B and T lymphocytes, leading to long-lasting immunity.