Which are the types of neurons that participate in the spinal arch reflex? Where are their cell bodies situated?

In the arch reflex first a sensory neuron located in the ganglion of a dorsal spinal root collects the stimulus information from the tissues. This sensory neuron makes direct or indirect (by interneurons) connection with inferior motor neurons of the spinal cord. These motor neurons then command the reflex reaction. So sensory neurons, interneuron motor neurons participate in the arch reflex.