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. 2004 May;72(5):2538–2545. doi: 10.1128/IAI.72.5.2538-2545.2004

FIG. 4.

FIG. 4.

Cohort challenge and prechallenge anti-C. abortus serum IgM levels strongly modulate fertility after uterine challenge with C. abortus. Fertility of challenged heifers (i.e., the percentage of pregnant animals) is significantly predicted in logistic regression models by the uterine C. abortus inoculum dose and cohort challenge by C. abortus (A) or by the uterine inoculum dose and concentration of preformed IgM against C. abortus (B). The solid line represents fertility dependence on the uterine inoculum under conditions of cohort challenge to C. abortus (A) or under conditions of below-median (low) levels of anti-C. abortus IgM (B). The dashed line represents fertility without cohort challenge (A) or with above-median (high) levels of anti-C. abortus IgM (B). The graphs represent logistic regression equations: % pregnant heifers (probability of pregnancy) = 100 [e10.56 − 1.68(log IFU) − 1.53(C)/ (1 + e10.56 − 1.68(log IFU) − 1.53(C))] (A) or % pregnant = 100 [e8.73 − 1.21(log IFU) − 1.48(IgM)/(1 + e8.73 − 1.21(log IFU) − 1.48(IgM))] (B), where log IFU represents the log10 of the uterine inoculum IFU dose of C. abortus, C represents either no (0) or cohort (1) challenge by C. abortus, and IgM represents an either below-median (0) or above-median (1) concentration of preformed anti-C. abortus IgM. The Wald P values are as follows: for inoculum dose, 0.016 (A) and 0.024 (B); for cohort challenge, 0.048; and for IgM levels, 0.043. These logistic regression models of fertility of heifers with established immunity against C. abortus indicate that (i) with cohort challenge a uterine infection of 105.38 IFU of C. abortus is necessary to reduce fertility of heifers from 100 to 50% compared to the 8.5-fold-higher dose of 106.31 IFU required for the same reduction without cohort challenge (A) and (ii) at low prechallenge anti-C. abortus IgM levels 106.01 intrauterine IFU of C. abortus reduce fertility of heifers from 100 to 50% compared to the 17-fold-higher dose of 107.24 IFU required for the same reduction at high prechallenge anti-C. abortus IgM levels (B).