Transposable elements (TE) constitute up to two-thirds of mammalian genomes, and the presence of DNA regulatory regions within them has led to the hypothesis that TEs have been co-opted to regulate mammalian gene expression and cell phenotype. Our group has shown that the long interspersed nuclear element (LINE) Lx9c11 regulates the immune response to virus infection in mice. In this study, we asked whether other LINE-1s might act as immune modulators by targeting DNA regulatory regions within the LINE-1 sequence of interest. To do this, we performed a CRISPR-Cas9 screen of immune cell subsets. Our dataset included LINE-1s upstream (<10,000 bases) of genes overexpressed upon immune stimulation and those exhibiting positive selection signatures in conservation analyses. CRISPR-Cas9 guides were selected that targeted 24,968 LINE-1’s in total, designed with cutting sites at regulatory regions; including transcription factor binding sites, CTCF binding sites, enhancers and splice sites. Next, we delivered CRISPR-Cas9 constructs into THP-1 monocytes, stimulated with LPS, and performed flow cytometry and FACS analyses to identify cells with altered activation phenotypes. This approach identifies LINEs with immune regulatory roles and demonstrates the feasibility of genome-wide approaches to targeting repetitive elements in the human genome for functional validation.