Hi Heba,

you may consider following reasons:

- electrophoresis problems, e.i. quality of gel or Laemli sample loading buffer (better to use a fresh one) 

- if the first problem is excluded, you may think about proteolysis. Thus, you have to use protease inhibitors and perform WB as soon as possible after sample preparation.

- post-translational modification(s) of you protein. If so,  it has to be studied in details and can be a big peace of work.

 Good luck.

Hi Heba,

In a technical point of View:

1) Before considering the said bands, first I would ask you how much specific they are? 

2) if any other non-specific bands present along with them, then consider the relative intensity of these two bands

3) may I know the detection method (HRP or IR dye based)?

4) What have you changed while doing western after stripping the blot?

In the biological point of view:

1) I also agree with Dr.Shalak, that it could be a PTM or proteolysis. Don't ignore the possibility of isoforms.

2) How much consistent with other individual repeats?

Good luck..!