Mucosal and systemic antibody formation in the rat after intranasal administration of three different antigens

In order to study the role of nasal-associated lymphoid tissue (NALT) in the local nasal immune response, rats were immunized intra-nasally with either of the following trinitrophenylated (TNP) antigens; the thymus-dependent keyhole limpet haemocyanin (KLH), or the thymus-independent lipopolysaccharide (LPS), or with the particulate (thymus-dependent) sheep red blood cells (SRBC). Primary responses hardly occurred, while only TNP-KLH elicited a considerable secondary response. The major responding organ was the posterior cervical lymph node. Specific antibody-forming cells (AFC) occurred in the medulla and were mainly of the IgA or IgG isotype. Hardly any specific AFC were found in NALT or the surrounding mucosa. Intranasal immunization evoked no antibody response in the lung. Ample anti-TNP antibodies could be detected in the sera of animals, primed and boosted with TNP-KLH or TNP-LPS. No specific serum antibodies occurred after immunization with TNP-SRBC. The results are discussed in view of the immunological defence in the upper respiratory tract.