Changes in cat specific IgE and IgG antibodies with decreased cat exposure.

BACKGROUND

Current understanding of the effects of reducing exposure to cat allergens is limited. It has also become clear that there are different forms of immune response to cat allergens.

OBJECTIVE

To investigate changes in skin tests and cat specific IgG and IgE antibodies when students from a home with a cat move to a college dormitory.

METHODS

Ninety-seven college students participated in a prospective study that consisted of allergy skin prick testing and serum measurement of IgE and IgG antibodies to cat at the beginning and end of one academic year in college. A subgroup returned for follow-up at the end of 2 years.

RESULTS

Among 97 students, 33% had IgG antibodies to Fel d 1 but no evidence of sensitization, 25% had positive skin test results and/or serum IgE antibodies, and 42% had negative skin test results and no detectable serum antibodies. Among the non-cat sensitized students with IgG antibodies, the titers decreased during 8 months (P = .002). Titers of IgG4 to Fel d 1 also decreased (P < .001). Among the sensitized students, no change in IgE antibodies to cat occurred in 8 months (P = .20), whereas Fel d 1 specific IgG antibodies decreased (P < .001). Thus, ratios of IgG to IgE decreased highly significantly (P = .007). Among the students with negative skin test results who returned for follow-up (n = 56), none developed positive skin test results or serum IgE antibodies.

CONCLUSION

Under conditions of marked decrease in exposure, no participants developed new-onset sensitization. Among the individuals sensitized at study entry, there were major decreases in the ratio of IgG to IgE.