[Intermolecular antigenic competition. Influence of the site of antigen injection (author's transl)]

We have studied the intermolecular antigenic competition in mice, after simultaneous injections of two antigens by different ways and in various places. When the two antigens are administered by I.P. route, and when TNP-SHRBC (Test-Ag) and BSA (inhibitory Ag) are used, only an inhibition of the anti-hapten (TNP) response is observed but not of the anti-carrier response (SRBC). When these antigens are replaced by SRBC (Test Ag) and HRBC (inhibitory Ag), there is no antigenic competition. When the inhibitory Ag is the BSA and the test Ag a strong dose of LPS (10 mug) there is no competition but it occurs when a weak dose of LPS is used. When the two antigens are injected by subcutaneous route in the same leg and the PFC enumerated in the corresponding inguinal lymph-node there is no inhibition but an increased response against the test Ag. On the contrary, competition is obtained when the test Ag (TNP-SHRBC or SRBC) is injected in the right leg and the inhibitory-Ag (BSA or HRBC) in the left one. These facts lead to conclude that an inhibitory humoral factor is responsible for this phenomenon, and that this factor is probably thymodependent because this competition disappears when Nude mice are used.