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Using 6 fractions differing in molecular weight of Dermatophagoides pteronyssinus (Dp)-antigen, we measured by enzyme-linked immunosorbent assay (ELISA) the titers of specific IgE, IgG and IgG4 antibodies against Dp antigen in sera of allergic subjects who were sensitive to house dust mite. We intended to evaluate which Dp fraction acts as the major antigenicity for allergic subjects. Results were as follows: 1) In comparison with normal controls, the titer of IgE antibody specific to crude Dp antigen was evaluated, but no significant difference was found among the titers of IgE antibody against each Dp fraction. 2) The titer of IgG antibody against the fraction with a high molecular weight (190 KD, 95 KD) was significantly higher than the titer of the 15 KD fraction in the nasal allergy patients. 3) The 15 KD fraction induced significant elevation of the titer of IgG4 antibody. It suggests that the low molecular weight fraction may act as the major allergenicity of Dp-antigen for inducing both IgE and competitive IgG4 antibodies, although other fractions induce significant IgE responses in patients with nasal allergy.

Serum levels of total IgE, specific IgE, IgG and IgG4 against house dust mite were measured in mite-sensitive asthma patients receiving immunotherapy with house dust. Serum levels of total IgE, mite specific IgE and IgG did not significantly change during the course of hyposensitization. Increased levels of mite specific IgG4 were observed in patients during immunotherapy. The increase in specific IgG4 was dependent on the total dose of house dust administered in both children (r = 0.636, p less than 0.001) and adults (r = 0.629, p less than 0.01). However, the increase of specific IgG4 in adults was not as apparent as in children. These results might suggest that mite specific IgG4 is a useful immunological marker in the immunotherapy for allergic asthma, and that IgG4 antibody acts as a blocking antibody in atopic bronchial asthma.

We investigated the antibody dependent cell-mediated cytotoxicity (ADCC) of lymphocytes and monocytes toward human O+ red cells coated with anti-D antibody using a 51Cr release assay. Lysis of sensitized red cells by lymphocytes occurred rapidly, but monocyte-mediated lysis occurred slowly. This difference might be due to postphagocytic 51Cr release by monocytes. ADCC of lymphocytes increased in proportion to the effector cell number, but large amounts of antibodies were required. In contrast, ADCC of monocytes was independent of the effector/target ratio and very small amounts of antibodies could produce red cell lysis. Large amounts of fluid phase IgG were required to inhibit the lymphocyte ADCC, whereas the monocyte ADCC was markedly inhibited by small amounts of IgG. Monocyte-mediated lysis was completely inhibited by the addition of 10% human AB serum, but lymphocyte-mediated lysis was only slightly inhibited. Purified IgG1 and IgG3 were much more inhibitory to the lysis by both effectors than IgG2 and IgG4 (IgG2 greater than IgG4). Erythrophagocytosis also was inhibited by IgG1 and IgG3. These studies demonstrate that lymphocytes as well as monocytes can cause the lysis of antibody sensitized red cells, and IgG1 and IgG3 subclasses are more important than IgG2 and IgG4 in causing lysis of anti-D coated red cells.