Correlation of CCL28 Between CCR10 and CCR3

So this slides show you how the B cells or IgA producing plasma cells respond to the signals which is produced from the mammary gland of the mothers.

So, there are chemokines which have cell migration capacities. So far, more than 50 chemokines have been identified nd then one of chemokines named CCL28 has been known to be produced in the mammary gland. So if the cells respond to the CCL28 which is produced from the mammary gland, they initiate to infiltrate into the tissues like this. And in humans, it has been known that the receptor of CCL28 is either CCR10 or CCR3. We next wanted to understand when the CCL28 is expressed in the mammary gland throughout the reproductive cycles. Because we have data showing the number of IgA producing plasma cells in the mammary gland or we have data showing the concentration of IgA in milk.

So we have hypothesized that the CCL28 expressions in the mammary gland is elevated during lactations and leads to the maximum two weeks after parturition. And then after weaning, it is reduced dramatically. While in the forced weaning group, the expression level of CCL28 is also very low. We wanted to confirm our hypothesis. So we extracted messenger RNA from the mammary gland tissues throughout the lead productive cycle. And then we perform the quantitative PCR analysis to confirm the expression level of CCL28 in the mammary gland. This is the data. I think you notice that the data of expression profile is very similar to the number of IgA producing plasma cells in the mammary gland.

Because the expression level of CCL28 before pregnancy, during pregnancy, or just after parturition, it’s very low. And then after parturition, especially one-week parturition, two weeks after parturition, the level increased dramatically. And after weaning, in both the forced weaning group and normal weaning group, the expression level is very low. It looks like CCL28 is critical chemokines that recruit the IgA producing plasma cells into the mammary gland. So we next wanted to know what kind of receptor is involved in the recognition of CCL28. Again, as I told you, in humans, it has been known that two receptors named CCR10 and CCR3, both receptors can recognize the CCL28.

So we wanted to know in mice or in the mammary gland, which receptor is involved in the recognition of mammary gland derived CCL28. In this case, we use a knockout mice system. The one is CCR10 knockout mice, the other is CCR3 knockout mice. And the final one is double-knockout mice. CCR10 knockout mice mean they have an immune system. They can get babies, but the B cells or plasma cells cannot produce CCR10. That’s why even if they produce CCL28 which is the chemokines they cannot recognize the CCL28. So if CCR10, is essential for the recognition of mammary gland derived CCL28 they cannot produce milk IgA.

CCR3 knockout mice, they have an immune system normally, and they can get babies, but they cannot express CCR3 So using this kind of knockout mouse system, we can identify which receptor is essential for the recognition of CCL28. And this is the data of milk IgA protein. Wild-type (WT) means normal mice. Again, two weeks after parturition, wild type mice produce a very high level of IgA proteins in milk. But CCR10 knockout mice, or double-knockout mice, they cannot produce any IgA maternal antibodies in milk.

But CCR3 knockout mice, the amount of IgA protein in milk is almost comparable to the wild type mice indicating that CCL28 and CCR10 axis are critical for the recognition of CCL28 which is produced from the mammary gland.

Let me summarize. The B cells or plasma cells express CCR10. And then, the CCR10-expressing B cells, or plasma cells react to the CCL28 which is produced from the mammary gland during lactations. Then they start to migrate into the mammogram in order to produce maternal IgA antibodies.