Hopefully others post with their information and recommended information resources. Mayo Clinic also has some researchers engaged on this topic. There are many online information resources, especially presentations by the leading PCa immunotherapy researchers, that provide both general overviews and more details for each of the types of immunotherapies, including Dendritic Cell (DC).

I have researched DC therapies and other PCa immunotherapies. My information gathering included attending conferences and corresponding (email and phone) with some of the leading PCa focused researchers in the US and Europe, but is not exhaustive .... you can find better sources of information. Updates are ongoing.

My overall learning is to be wary of any clinics that market DC immunotherapies for curing PCa. If it was successful, it would logically be much more broadly used, independent of whether or not it is covered by the specific health care insurance. My learning includes various clinics across the world that state they have unique patient-customized therapies. Ask for statistical data on all PCa patients tested.

(1) DC based PCs immunotherapies have been around for over 20 years. In 2010, a DC based immunotherapy named Sipuleucel-T (marketed as Provenge) was approved in the US. However, you do not often read about it, because the results were minimal (a few months) life extension. This included trials using a combination of DC and Chemotherapies. Pembrolizumab (marketed a Keytruda), another type of immunotherapy that is not DC based, was approved for medical use in the United States in 2014 and more recently used for PCa patients. However, Keystruda has already only been shown to be effective in the approx 5% of PCa patients with a specific PD-1L mutation. There a many other forms of PCa-specific immunotherapies being developed, because Provenge and Keytruda have not been broadly successful.

(2) All immunotherapies are dependent upon the PCa tumor mutations and, as a result, one of the first steps in considering immunotherapies is testing of the specific mutations in a person's prostate cancer.

(3) You can find a listing of all PCa clinical trials underway in the UK and, more specifically, those based upon immunotherapies. It is a bit tedious. The UK has several trials underway that include Keystruda, based upon what I saw earlier today when I checked the URL Links.
https://www.cancerresearchuk.org/about-cancer/prostate-cancer/research-clinical-trials?
Perhaps more importantly, through the contacts managing the trials at various locations, you can often learn much about the status of other PCa-focused immunotherapies and trials.

There are several online communities of PCa patients that have undergone immunotherapy treatments and will be willing to share their experience. If you don't find better sources of information, please feel free to message me and I will forward more detailed information and/or links to resources.