Thank you so much in advance. I am curious if expression database (RNA seq or microarray) for immune cells exist. Also, is there a database exclusively for mouse?
Check for the keyword ImmGen. This is a consortium that has produced and published extensive transcriptome (array and NGS) and epigenomic (ATAC-seq) data for the majority of immune cell types of mice. Data are all accessable via NCBI. THey also have a website where you might get pre-analyzed files such as count tables but I personally prefer to download raw data from NCBI/ENA and re-analyze myself.