TLR4 deficient C3H/HeJ and control C3H/HeOuJ mice were administered OVA protein alone or OVA + Ti, seven days later challenged with OVA alone, and 21 days after final inoculation serum was collected from each mouse and individually assayed for total and Ag-specific Igs. Both total serum IgE (A) and IgG1 (B) were markedly elevated, while slight increases in total serum Ig2a (C) were observed. Similarly, OVA-specific IgE (D), IgG1 (E), and IgG2a (F) were elevated. Data are expressed as the mean and s.e. of 5 individual mice within each treatment group treated compared to the untreated (OVA) group). This experiment was repeated two times with similar results (**p<0.01).