I18n not working in plugin

The problem I was encountering was a result of not realizing that the 3rd parameter for load_plugin_textdomain should be a relative path to the language directory from WP_PLUGIN_DIR. Since plugin_dir_path returns an absolute path, things broke.

Changing the hooked function as follows solved the problem:

add_action('plugins_loaded', array('PluginName', 'loadTextDomain'));
class PluginName {
    public static function loadTextDomain() {
        load_plugin_textdomain('plugin-domain', false, dirname(plugin_basename(__FILE__ )) . '/languages/');
    }
}