Blocking LFA-1 Aggravates Cardiac Inflammation in Experimental Autoimmune Myocarditis

Abstract

The lymphocyte function-associated antigen 1 (LFA-1) is a member of the beta2-integrin family and plays a pivotal role for T cell activation and leukocyte trafficking under inflammatory conditions. Blocking LFA-1 has reduced or aggravated inflammation depending on the inflammation model. To investigate the effect of LFA-1 in myocarditis, mice with experimental autoimmune myocarditis (EAM) were treated with a function blocking anti-LFA-1 antibody from day 1 of disease until day 21, the peak of inflammation. Cardiac inflammation was evaluated by measuring infiltration of leukocytes into the inflamed cardiac tissue using histology and flow cytometry and was assessed by analysis of the heart weight/body weight ratio. LFA-1 antibody treatment severely enhanced leukocyte infiltration, in particular infiltration of CD11b+ monocytes, F4/80+ macrophages, CD4+ T cells, Ly6G+ neutrophils, and CD133+ progenitor cells at peak of inflammation which was accompanied by an increased heart weight/body weight ratio. Thus, blocking LFA-1 starting at the time of immunization severely aggravated acute cardiac inflammation in the EAM model.

Keywords: inflammation; leukocytes; myocarditis.

Figure 1

Blocking lymphocyte function-associated antigen 1 (LFA-1) aggravated cardiac inflammation in experimental autoimmune myocarditis (EAM): (a) Representative cross sections of heart tissue of sham-treated control mice, vehicle-treated EAM mice (PBS), anti-LFA-1-treated EAM mice as well as isotype control-treated mice on day 21. (b) EAM score (c) as well as evaluation of the heart weight/body weight ratio at day 21 after induction of EAM (EAM) or sham immunization (sham). EAM mice were treated with an anti-LFA-1 antibody (anti-LFA-1), a matching isotype control (isotype ctrl), or PBS as indicated, with n = 8 for sham group; n = 18 for EAM groups; * p < 0.05; ** p < 0.01; *** p < 0.001; n.s., not significant. Kruskal Wallis test followed by Dunn-Bonferroni post hoc test. Data are presented as (b) individual data points or (c) median with interquartile range, whiskers indicate 95% confidence interval.

Figure 2

Infiltration of different leukocyte subsets is enhanced by blocking LFA-1: Flow cytometric analysis of leukocyte subpopulations in the inflamed cardiac tissue on day 21 after induction of EAM. Diagrams display the percentage of leukocytes (a, CD45) and leukocyte subpopulations (b, CD4; c, CD45/CD11b; d, F4-80; e, CD45/CD11b/Ly6G; f, CD45/CD11b/CD133) of all cells after blocking LFA-1 (anti-LFA-1) compared with the matching isotype control antibody (isotype ctrl) or PBS. n = 18 for PBS, n = 17 for anti-LFA-1 and isotype ctrl. * p < 0.05; ** p < 0.01; *** p < 0.001; n.s., not significant. Kruskal Wallis test followed by Dunn-Bonferroni post hoc test. Data are presented as median with interquartile range, whiskers indicate 95% confidence interval.