• HLA-DRA1 belongs to the HLA class II alpha chain paralogues. HLA-DRB1 belongs to the HLA class II beta chain paralogues. This class II molecule is a heterodimer consisting of an alpha (HLA-DRA) and a beta (HLA-DRB) chain, both anchored in the membrane. It plays a central role in the immune system by presenting peptides derived from extracellular proteins. Class II molecules are expressed in antigen presenting cells (APC: B lymphocytes, dendritic cells, macrophages). The alpha chain is approximately 33-35 kDa and its gene contains 5 exons. The beta chain is approximately 26-28 kDa and its gene contains 6 exons.
• The exons 2-4 of mouse I-Ea1 gene that encode the extracellular and transmembrane domain were replaced by human counterparts in B-hHLA-DRB1*4.1 mice(C). The exons 2-4 of mouse I-Eb1 gene that encode the extracellular and transmembrane domain were replaced by human counterparts in B-hHLA-DRB1*4.1 mice(C).  The  mouse I-Aa, I-Ab and I-Eb2 were knocked out in B-hHLA-DRB1*4.1 mice(C). 
• Human HLA-DR was exclusively detectable in homozygous B-hHLA-DRB1*4.1 mice(C), but not in wild-type BALB/cCrSIcNifdc mice.
• B-hHLA-DRB1*4.1 mice(C) provide a powerful preclinical model for in vivo evaluation of vaccines.
• Application: For example, this product is used for pharmacodynamics and safety evaluation of vaccines for cancers.

Gene targeting strategy for B-hHLA-DRB1*4.1 mice(C). The exons 2-4 of mouse I-Ea1 gene that encode the extracellular and transmembrane domain were replaced by human counterparts in B-hHLA-DRB1*4.1 mice(C). The exons 2-4 of mouse I-Eb1 gene that encode the extracellular and transmembrane domain were replaced by human counterparts in B-hHLA-DRB1*4.1 mice(C).  The  mouse I-Aa, I-Ab and I-Eb2 were knocked out in B-hHLA-DRB1*4.1 mice(C). 

Strain specific mH2-A/H2-E expression analysis in wild-type BALB/cCrSIcNifdc mice by flow cytometry. Splenocytes, blood cells and bone marrow cells were collected from wild-type BALB/cCrSIcNifdc mice (+/+), and analyzed by flow cytometry with species-specific anti-mouse H2-A/H2-E antibody(Biolegend, 107607). Mouse H2-A/H2-E was only detectable in immune cells of wild-type mice but not in immune cells of B-hHLA-DRB1*4.1 mice(C) (The page 6).

Strain specific mH2-A/H2-E expression analysis in B-hHLA-DRB1*4.1 mice(C) by flow cytometry. Splenocytes, blood cells and bone marrow cells were collected from B-hHLA-DRB1*4.1 mice(C), and analyzed by flow cytometry with species-specific anti-mouse H2-A/H2-E antibody(Biolegend, 107607). Mouse H2-A/H2-E was not detectable in immune cells of B-hHLA-DRB1*4.1 mice(C).

Strain specific HLA-DR expression analysis in wild-type BALB/cCrSIcNifdc mice by flow cytometry. Splenocytes, blood cells and bone marrow cells were collected from wild-type BALB/cCrSIcNifdc mice (+/+), and analyzed by flow cytometry with species-specific anti-HLA-DRB1 antibody(Biolegend, 307624). Human HLA-DR was not detectable in immune cells of wild-type mice but exclusively in immune cells of B-hHLA-DRB1*4.1 mice(C) (The page 8).

Strain specific HLA-DR expression analysis in B-hHLA-DRB1*4.1 mice(C) by flow cytometry. Splenocytes, blood cells and bone marrow cells were collected from B-hHLA-DRB1*4.1 mice(C), and analyzed by flow cytometry with species-specific anti-HLA-DR antibody(Biolegend, 307624). Human HLA-DR was only detectable in immune cells of B-hHLA-DRB1*4.1 mice(C).

Frequency of leukocyte subpopulations in the spleen by flow cytometry. Splenocytes were isolated from wild-type BALB/cCrSlcNifdc mice and homozygous B-hHLA-DRB1*4.1 mice(C) (Female,8-week-old, n=3). A. Flow cytometry analysis of the splenocytes was performed to assess the frequency of leukocyte subpopulations. B. Frequencies of T cell subpopulations. Frequencies of NK cells, DCs, neutrophils, monocytes, macrophages, and Tregs in B-hHLA-DRB1*4.1 mice(C) were similar to those in BALB/cCrSlcNifdc mice. The frequency of B cells was significantly increased, while the frequency of T cells was significantly decreased. The frequency of CD8+ T cells in B-hHLA-DRB1*4.1 mice(C) was significantly increased, while the frequency of CD4+ T cells were significantly decreased, demonstrating that humanized mice modification affects the proportion of T cell subtypes in the spleen. Values are expressed as mean ± SEM. Significance was determined by two-way ANOVA test.  *P < 0.05, **P < 0.01, ***P < 0.001. 

Frequency of leukocyte subpopulations in the blood by flow cytometry. Blood cells were isolated from wild-type BALB/cCrSlcNifdc mice and homozygous B-hHLA-DRB1*4.1 mice(C) (Female,8-week-old, n=3). A. Flow cytometry analysis of the blood was performed to assess the frequency of leukocyte subpopulations. B. Frequency of T cell subpopulations. Frequencies of NK cells, DCs, neutrophils, monocytes, macrophages, and Tregs in B-hHLA-DRB1*4.1 mice(C) were similar to those in BALB/cCrSlcNifdc mice. The frequency of B cells was significantly increased, while the frequency of T cells was significantly decreased. The frequency of CD8+ T cells in B-hHLA-DRB1*4.1 mice(C) was significantly increased, while the frequency of CD4+ T cells was significantly decreased, demonstrating that humanized mice modification affects the proportion of T cell subtypes in the blood. Values are expressed as mean ± SEM. Significance was determined by two-way ANOVA test.  *P < 0.05, **P < 0.01, ***P < 0.001.